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Chemical Reactions & Equations ( Top 25 questions)

Chemical Reactions and Equations

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

Sodium reacts with water to form sodium hydroxide and hydrogen gas.
The balanced equation which represents the above reaction is
1. Na(s) + 2H2O(l) → 2NaOH(aq) + 2H2(g)
2. 2Na(s) + 2H2O(l) → 2NaOH(aq) +H2(g)
3. 2Na(s) + 2H2O(l) → NaOH(aq) + 2H2(g)
4. 2Na(s) + H2O(l) → 2NaOH(aq) + 2H2(g)
Assertion (A) : Following is a balanced chemical equation for the action of steam on iron :
3Fe + 4H20 → Fe3O4 + 4H2
Reason (R): The law of conservation of mass holds good for a chemical equation.
1. Both (A) and (R) are true and reason (R) is the correct explanation of the assertion (A).
2. Both (A) and (R) are true, but reason (R) is not the correct explanation of the assertion (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
When aqueous solutions of potassium iodide and lead nitrate are mixed, an insoluble substance separates out. The chemical equation for the reaction involved is
1. KI + PbNO3 → PbI + KNO3
2. 2KI +Pb(NO3)2 → PbI2 + 2KNO3
3. KI + P(NO3)2 → PbI+ KNO3
4. KI + PbNO3 → PbI2 + KNO3
A metal ribbon ‘X’ burns in oxygen with a dazzling white flame forming a white ash ‘Y’ The correct description of X, Y and the type of reaction is
1. X= Ca; Y= CaO;
  Type of reaction = Decomposition
2. X= Mg; Y = MgO;
  Type of reaction = Combination
3. X = AI; Y = Al2O3;
  Type of reaction = Thermal decomposition
4. X=Zn; Y= ZnO;
  Type of reaction = Endothermic
The balanced chemical equation showing reaction between quick lime and water is
1. 2Ca0 + H2O → 2CaOH + H2 + Heat
2. CaO + H2O → Ca(OH)2 + H2 + Heat
3. CaO+H2O → Ca(OH)2 + Heat
4. 2Ca0 + 3H20 → 2Ca(OH)3 + 02 + Heat
Study the following chemical reaction:
2N3(s) + 2H20(l) → 2NaOH(aq) + H2(g)↑
The reducing agent in this reaction is
1. Na
2. H2O
3. NaOH
4. H2
Assertion (A): In the following reaction ZnO + C → Zn + CO
ZnO undergoes reduction.
Reason (R): Carbon is a reducing agent that reduces ZnO to Zn.
1. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A)
2. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A)
3. Assertion (A) is true, but Reason (R) is false.
4. Assertion (A) is false, but Reason (R) is true.
Which of the following statement about the reaction given below are correct?
MnO2 + 4HCI → MnCl2 + 2H20 + CI2
1. HCI is oxidized to Cl2-
2. MnO2 is reduced to MnCl2-
3. MnCl2 acts as an oxidizing agent
4. HCI acts as an oxidizing agent
  1. (ii), (ii) and (iv)
  2. (i), (ii) and (iii)
  3. (i) and (ii) only
  4. (iii) and (iv) only
A student took sodium sulphate solution in a test tube and added barium chloride solution to it. He observed that an insoluble substance has formed. The colour and molecular formula of the insoluble substance is
1. grey, Ba2S04
2. yellow, Ba(S04)2
  1. white, Bas04
  2. pink, BaSO4
When lead nitrate powder is heated in boiling tube, we observe
1. brown fumes of nitrogen dioxide
2. Brown fumes of lead oxide
3. Yellow fumes of nitrogen dioxide
4. Brown fumes of nitric oxide
When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a
1. combination reaction
2. displacement reaction
3. decomposition reaction
4. double displacement reaction
Which one of the following reactions is categorized as thermal decomposition reaction?
1. 2H2O(l) → 2H2(l) + 02(g)
2. 2AgBr(s) → 2Ag(s) + Br2(g)
3. 2AgCl(s) → 2Ag(s) + Cl2(g)
4. CaCO3(g) → CaO(s) + CO2(g)
Assertion (A) : Silver salts are used in black and white photography. Reason (R): Silver salts do not decompose in the presence of light.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Calcium oxide reacts vigorously with water to produce slaked lime.
CaO(s) + H2O(l) → Ca(OH)2(aq)
This reaction can be classified as
1. combination reaction
2. exothermic reaction
3. endothermic reaction
4. oxidation reaction.
  Which of the following is a correct option?
  1. (A)and (C)
  2. (C) and (D)
  3. (A), (C) and (D)
  4. (A) and (B)
Copper utensils slowly lose their shiny brown surface and gain a green coat on prolonged exposure to atmospheric air. This is due to the formation of a coating of
1. copper sulphate
2. copper carbonate
3. cupric oxide
4. cuprous oxide.
  SHORT AND LONG QUESTIONS
Balance the following chemical equations.
1. BaCl2 + H2SO4 → BaSO4 + HCl
2. Ca(OH)2 + HNO3 → Ca(NO3)2 + H2O
3. Pb(NO3)2 → PbO + NO2 + O2
(d)MnO2 +HCl → MnCl2 +H2O+Cl2
A zinc plate was put into a solution of copper sulphate kept in a glass container. It was found that blue colour of the solution gets fader and fader with the passage of time. After few days, when zinc plate was taken out of the solution, a number of holes were observed on it.
1. State the reason for changes observed on the zinc plate.
2. Write the chemical equation for the reaction involved.
You might have noted that when copper powder is heated in a china dish, the surface of copper powder becomes coated with a black colour substance.
1. How has this black coloured substance formed?
2. What is that black substance?
3. Write the chemical equation of the reaction that takes place.
Name the reducing agent in the following reaction: 3MnO2 + 4Al → 3Mn + 2Al2O3
State which is more reactive, Mn or Al and why?
What is the colour of ferrous sulphate crystals? How does this colour change after heating? Answer
Why does the colour of copper sulphate solution change when an iron nail is dipped in it? Write two observations.
What is rancidity? Mention any two ways by which rancidity can be prevented.
COMPETENCY BASED QUESTIONS
Take about 2 g ferrous sulphate crystals in a dry boiling tube. Heat the boiling tube over the flame of a burner or spirit lamp. In this reaction you can observe that a single reactant breaks down to give simpler products. This is a decomposition reaction. Ferrous sulphate crystals (FeSO4, 7H2O) lose water when heated and the colour of the crystals changes. It then decomposes to ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide (SO3). Ferric oxide is a solid, while SO2 and SO3 are gases.
1. What can we observe in this activity?
  1. Water vapor is evolved
  2. Change in colour
  3. Smell of burning sulphur
  4. All of the above.
2. What is the colour of iron oxide? A.Brown
  B.Grey C.Yellow D.White
3. What compound is formed when sulphur dioxide is passed through water?
  1. Sulphuric acid B.Sulphurous acid
1. Hydrogen Sulphide
2. Sulphur trioxide
Read the following and answer the questions:
The double displacement reaction is a type of chemical reaction. where two compounds react and the cation and anion of the two reactants 6 places forming 2 new products. The ionic compounds considered as reactants are water soluble. One of the products is formed as a precipitate or as a gas which is water soluble.
1. The reaction between lead nitrate and potassium iodide is an example of:
  1. Combination reaction
  2. Decomposition Reaction
  3. Displacement reaction
  4. Double displacement reaction.
2. What was the color of the precipitate formed when Lead nitrate reacts with Potassium iodide ?
  1. Blue
  2. Red
  3. Yellow
  4. Orange
3. Which metallic spoon can be used to stir Lead nitrate solution ? A)Sodium
1. Silver
2. Iron
3. Aluminum
We have observed that iron articles are shiny when new, but get coated with a reddish brown powder when left for some time. This process is commonly known as rusting of iron. Some other metals also get tarnished in this manner. Have you noticed the colour of the coating formed on copper and silver? When a metal is attacked by substances around it such as moisture, acids, etc., it is said to corrode and this process is called corrosion.

The chemical formula of rust is
1. Fe2O3
2. Fe3O4
3. Fe2O3 XH2O
4. Fe3O4. XH2O
Which of the following metal is highly corrosive ?
1. Zinc
2. Aluminum
3. Gold
4. Silver
If a metal under goes uniform corrosion it becomes
1. Thicker
2. Perforated
3. Thinner
4. None of the above
  SOLUTIONS:
  1. The balanced equation is
    (b) 2Na(s) + 2H2O(l) → 2NaOH(aq) +H2(g)
  2. (a) A balanced chemical equations must obey the law of conservation of mass.
  3. (b) 2KI +Pb(NO3)2 → PbI2 ↓ + 2KNO3
    (yellow ppt)
  4. (b) Magnesium metal, Mg(X) burns in oxygen with a dazzling white flame forming a whit ash, MgO(Y)
    2Mg + O2 → 2MgO
    This type of reaction is combination reaction.
  5. (c)Quick lime reacts vigorously with water to produce calcium hydroxide (slaked lime) and release a large amount of heat (exothermic reaction).
    CaO(s) + H2O(l) → Ca(OH)2 (aq) + heat (quick lime) (slaked lime)
  6. Oxidation
    1. 2Na + 2H2O → 2NaOH + H2
      Reduction
      Here, Na is oxidised to NaOH and H2O is reduced to H2. Na reacts as a reducing agent and H2O acts an oxidising agent.
  7. The reaction in which Oxygen is added or hydrogen is removed or loss of electrons takes place is called an oxidation reaction.
    In the reaction,
    Reduction
    1. 2Na + 2H2O → 2NaOH + H2
      xidation
  8. (c) Reduced
    MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
    Oxidised
    As hydrogen is removed from HCl to give Cl2, HCl is being oxidised whereas oxygen is removed from MnO2 to give MnCl2, hence MnO2 is reduced. Here MnO2 acts as an oxidising agent and HCl acts as a reducing agent.
  9. (c) The reaction between sodium sulphate and barium chloride is an example of double displacement reaction or precipitation reaction in which white ppt. of BaSO4 is obtained,
    Na2SO4 + BaCl2 → 2NaCl + BaSO4↓
    (white ppt)
  10. (a) When lead nitrate is heated in a boiling tube, brown fumes of nitrogen dioxide are found to evolve and a yellow residue of lead oxide is
    left behind in the test tube.
    2Pb(NO3)2(s) --Δ→ 2PbO(s) + 4 NO2(g) + O2(g)
    (white) (yellow (brown residue) fumes)
  11. (d) CuSO4 + H2S → CuS + H2SO4
    It is a double displacement reaction as in this reaction CuSO4 and H2S are reacting by exchange of Cu2+ and H+ ions to form two new compounds i.e., CuS and H2SO4.
  12. (d)

2H2O(l) → 2H2(l) + 02(g)
2AgBr(s) → 2Ag(s) + Br2(g)
2AgCl(s) → 2Ag(s) + Cl2(g)
CaCO3(g) → CaO(s) + CO2(g) - Thermal Decomposition

13.(c) Silver salts are used in black and white photography and they decompose in presence of sunlight.

2AgCl(s) ---su-n-li-gh-t-→ 2Ag(s) + Cl2(g)

(d) The reaction between CaO and HO to form Ca(OH)2 is an exothermic and combination reaction.
(b) 2Cu(s) + CO2(g) + O2(g) + H2O(l) → CuCO3.Cu(OH)2
Moisture Basic copper carbonate (green)
Air
(a) BaCl2 + H2SO4 → BaSO4 + 2HCl
1. Ca(OH)2 + 2HNO3 → Ca(NO3)2 + 2H2O
2. 2Pb(NO3)2 → 2PbO + 4NO2 + O2
3. MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(i) It is because zinc has displaced copper from CuS04. Zinc metal has been used to form zinc sulphate, therefore, number of holes were observed.
(ii) Zn(s) + CuSO4(aq) → ZnSO4(aq) +Cu(s)
Blue colourless
(i) Copper reacts with oxygen to form copper oxide which is black, i.e. oxidation of copper takes place.
1. Copper oxide
2. 2Cu(s) + O2(g) → 2CuO(s)
‘Al’ is reducing agent. ‘Al’ is more reactive than Mn v ‘Al’ displaces Mn from its oxide.
The colour of ferrous sulphate is pale green. The colour changes to reddish brown on heating due to formation of iron (III) oxide.
Give an example each for thermal decomposition and photochemical decomposition reactions.
Write relevant balanced chemical equations also. Thermal decomposition reaction:
CuCO3 (s) --H-e-a-t→ CuO(s) + CO2(g)
(green) (black)
Photochemical decomposition reaction: 2AgCl(s) -S-u-n-l-ig-h-t→ 2Ag(s) + Cl2(g)
It is because displacement reaction takes place. Iron displaces copper from copper sulphate solution and forms pale green coloured solution of FeS04 and reddish brown copper metal gets deposited.
Fe(s) + CuS04(aq) ——–> FeS04(aq) + Cu(s)
The process in which taste and smell of food gets spoiled is called rancidity. It happens due to oxidation. Prevention from rancidity: (i) Antioxidants are added to fatty acids to prevent oxidation, e.g. chips are packed in presence of nitrogen gas which prevents spoilage by oxidation. (ii)Food should be kept in airtight container in refrigerator.
1.D
2.A
3.C
1.D
2.C
3.B
1.C
2.B
3.C
Metals and Non Metals
TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS
1. Which of the following statements is true for an amphoteric oxide?
  1. It reacts only with acid and does not form water.
  2. It reacts with acid as well as base to form salt and hydrogen gas.
  3. It reacts with both acid as well as base to form salt and water.
  4. It reacts only with base and does not form water.
2. The pair(s) which will show displacement reaction is/are
  1. NaCl solution and copper metal
  2. AgNO3 solution and copper metal
  3. Al2(SO4)3 solution and magnesium metal
  4. ZnSO4 solution and iron metal.
    1. (ii) only
    2. (ii) and (iii)
    3. (iii) and (iv)
    4. (i) and (ii)
      
      Read the passaofte oftiven below and answer the followinoft questions from 3 to 6:
      A student, took four metals P, Q, R and S and carried out different experiments to study the properties of metals. Some of the observations were:
      1. All metals could not be cut with knife except metal R.
      2. Metal P combined with oxygen to form an oxide M2O3 which reacted with both acids and bases.
      3. Reaction with water:
  P-Did not react either with cold or hot water but reacted with steam.
  Q-Reacted with hot water and the metal started floating
  R-Reacted violently with cold water.
  S-Did not react with water at all
  Based on the above observations answer the following.
3. Out of the given metals, the one which needs to be stored in kerosene is
  a) P
  b) R
  c) S
  d) Q
4. Out of the given metals, the metal Q is
  1. iron
  2. zinc
  3. potassium
  4. magnesium
5. Metal which forms amphoteric oxides is
  1. P
  2. Q
  3. R
  4. S.
6. The increasing order of the reactivity of the four metals is
  1. P<Q<R<S
  2. S<R<Q<P
  3. S<P<Q<R
  4. P<R<Q<S.
7. Assertion (A): The solution of ionic compounds are good conductors of electricity.
  Reason (R): Movement of atoms of elements take place in solution.
  1. Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
  3. (A) is true, but (R) is false.
  4. (A) is false, but (R) is true.
8. Assertion (A): The metals and alloys are good conductors of electricity.
  Reason (R): Bronze is an alloy of copper and tin and it is not a good conductor of electricity.
  1. Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
  3. (A) is true, but (R) is false.
  4. (A) is false, but (R) is true.
9. Which one of the following statements is true about the position of metals in the activity series of metals?
  1. Copper is below hydrogen but above lead.
  2. Iron is below lead and zinc.
  3. Zinc is below magnesium but above aluminum.
  4. Magnesium is below calcium but above aluminum.
10. Select the correct matching in the following table in connection with the given chemical reaction
  
  Pale green
  
  Pale green

CuSO4 + Fe -> FeSO4 + Cu

SHORT AND LONG QUESTIONS

A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
Name any one metal which reacts neither with cold water nor with hot water, but reacts with heated steam to produce hydrogen gas.
Name the metal which reacts with a very dilute HNO3 to evolve hydrogen gas.
Arrange the following metals in the decreasing order of reactivity: Na, K, Cu, Ag.
An element forms an oxide, A2O3 which is acidic in nature. Identify A as a metal or nonmetal.
Name the following:
1. A metal, which is preserved in kerosene.
2. A lustrous coloured non-metal.
3. A metal, which can melt while kept on palm.
4. A metal, which is a poor conductor of heat.
Write two differences between calcination and roasting.
Write chemical equations that shows aluminium oxide reacts with acid as well as base.
Give reasons for the following observations:
1. Ionic compounds in general have high melting and boiling points.
2. Highly reactive metals cannot be obtained from their oxides by heating them with carbon.
3. Copper vessels get a green coat when left exposed to air in the rainy season.
State reasons for the following:
1. Electric wires are covered with rubber like material.
2. From dilute hydrochloric acid, zinc can liberate hydrogen gas but copper cannot.
3. Sulphide ore of a metal is first converted to its oxide to extract the metal from it.
a) The reaction of metal (X) with ferric oxide is highly exothermic. Metal (X) is obtained from its oxide by electrolytic reduction. Identify (X) and write its reaction with ferric oxide.
1. Give reason to justify that aluminium oxide is an amphoteric oxide. Also, give another example of amphoteric oxide.
2. Mention constituent metals present in bronze.
Give reasons for the following:
1. Silver and copper lose their shine when they are exposed to air. Name the substance formed on their surface in each case.
2. Tarnished copper vessels are cleaned with tamarind juice.
3. Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air.
Write balanced equations for the reaction of:
1. aluminium when heated in air. Write the name of the product.
2. iron with steam. Name the product obtained.
3. calcium with water. Why does calcium start floating in water?
What is cinnabar? How is metal extracted from cinnabar? Explain briefly.
What is an alloy? State the constituents of solder. Which property of solder makes it suitable for welding electrical wires?

SOLUTIONS:

(c):Some metal oxides such as aluminium oxide and zinc oxide show amphoteric nature (acidic and basic both) and react with both acids as well as with alkalies to form salt and water. These are called amphoteric oxides.
Al2O3 (s) + 2NaOH (aq) -> 2NaAlO2 (aq) + H2O (l)
sodium meta-aluminate
Al2O3 (s) + 6HCl (aq) -> 2AlCl3 (aq) + 3H2O (l)
Aluminium chloride
(b): As copper metal is less reactive than sodium, no displacement reaction will occur between NaCl solution and copper metal. Similarly, zinc is more reactive than iron and hence cannot be displaced by iron. Copper can displace silver and magnesium can displace aluminium.
(b): Metal R is highly reactive. It can be cut with knife, it should be either lithium, potassium or sodium and must be stored in kerosene oil.
(d): Magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen gas.
Mg (s) + 2H2O (l) -> Mg(OH)2 (aq) + H2 (l)
Magnesium starts floating on water as bubbles of hydrogen stick to it and as bubbles move up, they pull magnesium with them.
(a): It is given that metal P combines with oxygen to form its oxide which reacts both with acids and bases, so oxide of P is amphoteric in nature.
(c): Reactivity of given metals can be analysed on the basis of their reaction with water. Since S does not react with water, it is least reactive while R is most reactive because it reacts vigorously even with cold water. Q reacts with hot water while P reacts with steam only. So, the reactivity order of metals is
S<P<Q<R.
(c): The solutions of ionic compounds are good conductors of electricity as the ions of compound becomes free to move and conduct electricity.
(d): Metals have free electrons in them which can move freely inside them, so they conduct electricity very easily. Bronze is an alloy of copper and tin and it is not a good conductor of electricity.
(d)
(d): CuSO4 + Fe → FeSO4 + Cu
(Blue) (Pale green)
The above reaction is a displacement reaction in which iron being more reactive, displaces copper from CuSO4 solution, resulting into pale green solution of FeSO4.
‘X’ is carbon, ‘Y’ is diamond as it is the hardest natural substance and ‘Z’ is graphite as it is good conductor of electricity.
Iron
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
Magnesium
K > Na > Cu > Ag
‘A’ is non-metal as non-metallic oxides are acidic in nature.
(a) Sodium is preserved in kerosene.
1. Iodine is lustrous coloured non-metal.
2. Gallium.
3. Lead.
Al2O3 + 6HCl -> 2AlCl3 + 3H2O Al2O3 + 2NaOH -> 2NaAlO2 + H2O
(i) Ionic compounds have high melting and boiling points due to strong force of attraction between oppositely charged ions.
1. It is because these metals themselves are strong reducing agents. Therefore, cannot be reduced by reducing agent like carbon.
2. Copper vessels react with CO2, O2 and moisture to form green- coloured basic copper carbonate [CuCO3.Cu(OH)2].
(i) It is because rubber is an insulator and does not allow current to flow through it.
1. Zinc is more reactive than hydrogen. Therefore, it can displace hydrogen from dilute HCl whereas copper cannot, because it is less reactive than hydrogen.
2. It is because it is easier to reduce oxide ore as compared to sulphide ore.
(a) ‘X’ is ‘Al’
2Al + Fe2O3 -> Al2O3 + 2Fe
1. AI2O3 reacts with acid as well as base therefore it is amphoteric oxide. Al2O3 + 2NaOH -> 2NaAlO2 + H2O
  Al2O3 + 6HCl -> 2AlCl3 + 3H2
  Zinc oxide is also an amphoteric oxide.
2. Bronze contains’ copper and tin.
(i) These metals get corroded. Silver forms black Ag2S (silver sulphide) and copper form greenish layer of basic copper carbonate
CuCO3. Cu(OH)2 .
1. Tamarind contains acid which reacts with basic copper carbonate and product gets dissolved and removed from copper vessel.
2. Aluminium forms oxide layer on its surface which does not further react with air.
(i) heat
4Al + 3O2 ---------> 2Al2O3
The product formed is aluminium oxide.
1. 3Fe + 4H2O (steam) ---------> Fe3O4 + 4H2
  The product obtained is iron(II) iron (III) oxide
2. Ca + 2H2O > Ca(OH)2 + H2
The bubbles of hydrogen stick to the surface of metal that is why it floats.
Cinnabar is HgS.
Mercury is obtained by roasting cinnabar. HgO formed is thermally unstable and gives mercury.

Mercury can be purified by distillation.
Alloy is a homogeneous mixture of two or more metals. One of them can be a non-metal also. Solder consists of lead and tin. It has low melting point which makes it suitable for welding electrical wires.

Acid, Base and Salts

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

When sodium bicarbonate reacts with dilute hydrochloric acid, the gas evolved is
1. Hydrogen; it gives pop sound with burning. matchstick.
2. Hydrogen; it turns lime water milky.
3. Carbon dioxide; it turns lime water milky.
4. Carbon dioxide; it blows off a burning match stick with a pop sound
Acid present in tomato is:
1. Methanoic acid
2. Acetic acid
3. Lactic acid
4. Oxalic acid
Which of the following options in the given table are correct?
1. (i) and (ii)
2. (i) and (iv)
3. (ii) and (iii)
4. iii) and (iv)
Sodium hydroxide is termed as alkali while ferric hydroxide is not because:
1. Sodium hydroxide is a strong base, while ferric hydroxide is a weak base.
2. Sodium hydroxide is a base which is soluble in water while ferric hydroxide is also a base but it is not soluble in water.
3. Sodium hydroxide is a strong base while ferric hydroxide is a strong acid.
4. Sodium hydroxide and ferric hydroxide both are strong base but the solubility of sodium hydroxide in water is comparatively higher than that of ferric hydroxide.
Consider the following compounds
I. HCI II. C2H5OH
III. C6H1206 IV. H2SO4
Which of these compounds do not conduct electricity in solution?
1. I and II
2. II and III
3. III and IV
4. I and IV
The name of the salt used to remove permanent hardness of water is
1. Sodium hydrogen carbonate (NaHCO3)
2. Sodium chloride (NaCl)
3. Sodium carbonate decahydrate (Na2CO3.10H2O)
4. Calcium sulphate hemihydrate (CaSO4. 1/2H2O)
Which of the following salts do not have the water of crystallisation?
1. Bleaching Powder (ii) Plaster of Paris
2. Washing soda (iv) Baking soda
  1. (ii) and (iv)
  2. (i) and (iii)
  3. (ii) and (iii)
  4. (i) and (iv)
Assertion (A): Sodium hydrogen carbonate is used as an ingredient in antacids.
eason (R): NaHCO3 is a mild non-corrosive basic salt.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
An aqueous solution of a salt shows an orange red colour when a drop of universal indicator is added to it. This salt is made up of
1. a strong acid and a strong base
2. a weak acid and a weak base
3. a strong acid and a weak base
4. a weak acid and a strong base
Given below is a reaction showing Chlor-alkali process 2NaCl(aq) + 2H2O(l) -> 2NaOH(aq) + Cl2(g) + H2(g)
(A) (B) (C)
The products A, B and C are produced respectively
1. at the anode, at the cathode, near the cathode
2. near the cathode, at the anode, at the cathode
3. at the cathode, near the cathode, at the anode
4. at the anode, near the cathode, at the cathode.
SHORT AND LONG QUESTIONS
Which bases are called alkalies? Give an example of alkalies.
Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid indicating the physical state of the reactants and the products.
What happens when chlorine is passed over slaked lime at 313K? Write chemical equation of the reaction involved and state two uses of the product obtained.
Curd is not kept in copper and brass utensils. Why?
Name the natural source of each of the following acid
(i) Citric acid (ii)Oxalic acid (iii)Lactic acid (iv)Tartaric acid
A student detected the pH of four unknown solution A, follows 11, 5, 7 and 2. Predict the nature of the solution.
State reason for the following statements:
B, C and D as
1. Tap water conducts electricity whereas distilled water does not.
2. Dry hydrogen chloride gas does not turn blue litmus red whereas dilute hydrochloric acid does.
3. During summer season, a milk man usually adds a very small amount of baking soda to fresh milk.
4. For a dilution of acid, acid is added into water and not water into acid.
5. Ammonia is a base but does not contain hydroxyl group.
(a) Identify the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this salt. Name the source from where it is obtained.
1. What is rock salt? Mention its colour and the reason due to which it has this colour.
2. What happens when electricity is passed through brine? Write the chemical equation for it.
What are strong and weak acids? In the following list of acids, separate strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.
State in brief the preparation of washing soda from baking soda. Write balanced chemical equation of the reaction involved.
What is baking soda chemically called? Give reaction involved in its preparation. Write one of its uses.
What is meant by ‘water of crystallisation’ of a substance ? Describe an activity to show that blue copper sulphate crystals contain water of crystallisation.
Name the products formed in each case when
1. hydrochloric acid reacts with caustic soda.
2. granulated zinc reacts with caustic soda.
3. carbon dioxide is passed into lime water.
a) A metal compound ‘X’ reacts with dil. H2SO4 to produce effervescence, The gas evolved extinguishes a burning candle. If one of the compound formed is calcium sulphate, then what is ‘X’ and the gas evolved? Also, write a balanced chemical equation for the reaction which occurred.
(b) (i) Name one antacid. How does it help to relieve indigestion in stomach?
(ii) A farmer treats the soil with quicklime or calcium carbonate. What is the nature of soil? Why does the farmer treat the soil with quicklime?
(a) Write the name given to bases that are highly soluble in water. Give an example.

How is tooth decay related to pH? How can it be prevented?
Why does bee sting cause pain and irritation? Rubbing of baking soda on the sting area gives relief. How?

SOLUTIONS:

(c) When sodium bicarbonate reacts with dilute hydrochloric acid, carbon dioxide gas is liberated. The reaction that occurs is shown below:
NaHCO3+HCI -> NaCl + H2O+CO2↑
Carbon dioxide when passed into lime water gives a milky solution. This is due to the formation of an insoluble suspension of calcium carbonate:
Ca(OH)2(aq) + CO2(g) -> CaCO3(s)+H2O(l)
(d): Oxalic acid is present in tomato.
(c) Orange is a natural source of citric acid while tamarind contains tartaric acid.
(b) Sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. are soluble in water, therefore they are termed as alkalies while bases like copper hydroxide, ferric hydroxide, aluminium hydroxide, etc. do not dissolve in water, therefore they are not termed as alkalies.
(b): HCI and H2SO4 are strong acid, give H+ ions in aqueous solution and conduct electricity. C2H5OH and C6H12O6 do not produce ions in aqueous solution and hence do not conduct electricity.
(c) Na2CO3.10H2O is used to remove permanent hardness of water. Washing soda (Na2CO3.10H2O) reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates, that can be removed by filtration and then water becomes soft.
(d): Bleaching powder: CaOCl2 Plaster of Paris : CaSO4.1/2H2O Washing soda : Na2CO3.10H2O Baking soda : NaHCO3
a): Sodium hydrogen carbonate is used as an antacid to neutralise the acidity in the stomach because it is mild non-corrosive basic salt.
(c): An orange red colour of universal indicator shows that the solution tested is acidic in nature that is, salt is composed of a strong acid and a weak base.
(b): When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide and this process is called chlor- alkali process.
Soluble bases are called alkalies, e.g. sodium hydroxide (NaOH).
Bleaching powder is formed.
313K
Ca(OH)2 + Cl2 ------> CaOCl2 + H2O
1. It is used as bleaching agent in paper and textile industries.
2. It is used as disinfectant in purification of drinking water.
Curd and sour substances contain acids which react with brass and copper vessels to form poisonous salts which are harmful for our health.
(i) Lemon and orange. (ii)Tomatoes and Guava. (iii)Sour milk (curd). (iv)Tamarind.
A is basic ‘B’ is acidic ‘C’ is natural and ‘D’ is strongly acidic.
(i) Tap water contains ions which conduct electricity, distilled water does not contain ions.
1. Dry HCl does not form ions but HCl gives H+ and Cl–.
2. Baking soda does not allow milk to change to lactic acid which makes milk sour.
3. Adding water to acid is highly exothermic. Therefore water is added to acid very slowly with cooling.
4. Ammonia dissolves in water and forms H– Therefore, it is basic in nature.
(a) HCl is acid and NaOH is base whose combination forms the common salt. Its formula is NaCl (Sodium chloride). It is obtained from sea water.
(b) Rock salt is the common name for the mineral “halite”. Its chemical formula is NaCl. It may be white or light blue or yellow depending upon impurities present in it.

(c) electrolysis
2NaCl + 2H2O > 2NaOH + H2 + Cl2
Strong acids are those acids which are completely ionised in aqueous solution. Weak acids are those which do not ionise completely in aqueous solution. Strong acid: HCl, HNO3, H2SO4 Weak acid: Citric acid, acetic acid, formic acid.
Sodium hydrogencarbonate (baking soda) on heating gives sodium carbonate which on recrystallisation gives washing soda.
heat
2NaHCO3 > Na2CO3 + CO2 + H2O
Baking soda on heating gives sodium carbonate which on crystallisation from aqueous solution gives washing soda, e.g.
Na2CO3 + 10H2O → Na2CO3 . 10H2O
Sodium hydrogen carbonate.

NH3 + CO2 + H2O + NaCl ------> NaHCO3 + NH4Cl
or
NaCO3 + CO2 + H2O > 2NaHCO3
It is used as an antacid.
The water molecules associated with a crystalline substance is called ‘water of crystallisation’.
To show crystalline salts contain water of crystallisation.

Materials Required: CuS04.5H20 (Blue vitriol), boiling tube, burner, cork, delivery tube, test tube, clamp stand.

Procedure:
1. Take 2g of CuS04.5H20 in a boiling tube fitted in a clamp stand.
2. Observe its colour. Fit it with cork and delivery tube bent at two right angles which dips into a test tube.
3. Heat crystals in boiling tube. ‘
4. Observe vapours being condensed in test tube.
5. Cool the crystals and add few drops of water into it.
Observation: Water vapours get condensed in a test tube and colour of blue crystals changes into white. On adding water to anhydrous copper sulphate, it changes into blue again.

Chemical Reaction:
heat
CuSO4.5H2O > CuSO4 + 5H2O
blue vitriol white

onclusion: Crystalline substances have water of crystallisation which are lost on heating.
(a) Sodium chloride and water are formed.

NaOH(aq) + HCl(aq) > NaCl(aq) + H2O(l)

sodium
hydrochloric
sodium
water
hydroxide
acid
chloride
1. Sodium zincate and H2 are formed
  
  Zn(s) +
  2NaOH(aq)
  --------------> Na2ZnO2(aq)
  +
  H2(g)
  Zinc
  sodium
  sodium
  
  hydrogen
  
  hydroxide
  zincate
  
  gas
2. Calcium carbonate and water are formed.
Ca(OH)2(aq) + CO2(g) --------------> CaCO3(s) + H2O(l)
lime water carbon calcium water dioxide carbonate
(white ppt.)
(a) ‘X’ is CaCO3 (calcium carbonate). The gas evolved is CO2.

CaCO3 + H2SO4(dil.) ---------> CaSO4 + H2O + CO2
calcium sulphate

(b) (i) NaHCO3 is antacid. It neutralizes excess of acid formed in the stomach.
(ii) The soil is acidic in nature. The farmer wants to make it neutral by adding quicklime which is good for crops.
Answer.(a) Alkali, e.g. NaOH (Sodium hydroxide).

Lower the pH, more will be tooth decay. Acid reacts with Ca3(PO4)2 and cause tooth decay. It can be prevented by brushing teeth after every meal.
It is due to formic acid. Sodium hydrogencarbonate (Baking soda) neutralises formic acid giving relief.

Carbon and its Compounds

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

The correct representation of covalent bonding in an oxygen molecule is

a)

b)

c)
d)
Assertion (A): Carbon has a strong tendency to either lose or gain electrons to attain noble gas configuration.
Reason (R): Carbon has four electrons in its outermost shell and has the tendency to share electrons with carbon or other elements.
1. Both (A) and (R) are true and (R) is the correct explanation of(A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Assertion (A): Following are the members of a homologous series: CH3OH, CH3CH2OH, CH3CH2CH2OH
Reason (R): A series of compounds with same functional group but differing by -CH2 unit is called homologous series.
1. Both (A) and (R) are true and (R) is the correct explanation of(A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Assertion (A): Esterification is a process in which a sweet smelling substance is produced.
Reason (R): When esters react with sodium hydroxide, an alcohol and sodium salt of carboxylic acid are obtained.
1. Both (A) and (R) are true and (R) is the correct explanation of(A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic.
The factories located near A and B are
1. Soaps and detergents factories near A and alcohol distillery near B.
2. Soaps and detergents factories near B and alcohol distillery near A.
3. Lead storage battery manufacturing factories near A and soaps and detergents factories near B.
4. Lead storage battery manufacturing factories near B and soaps and detergents factories near A.
To prepare soap fat/oil is heated with :
1. ester
2. acid
3. alkali
4. alcohol
Assertion (A) : Melting point and boiling point of ethanol are lower than that of sodium chloride.
Reason (R) : The force of attraction between the molecules of ionic compounds are very strong.
1. Both (A) and (R) are true and (R) is the correct explanation of(A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
  
  SHORT AND LONG QUESTIONS
Covalent compounds have low melting and boiling points. Why?
Draw the electron dot structure of the following:
1. Cyclohexane
2. Butane
State the reason why
1. carbon compounds have low melting and boiling points.
2. carbon compounds do not conduct electricity.
3. carbon can form only covalent compounds.
Name the following compounds:
a)
b)
The molecular formulae of two alkynes, A and B are CxH2 and C3Hy respectively.
1. Find the values of x and y.
2. Write the names of A and B.
Consider the following organic compounds:
1. (ii)
  1. Name the functional group present in these compounds.
  2. Write the general formula for the compounds of this functional group.
  3. State the relationship between these compounds and draw the structure of any other compound having similar functional group.
Write the molecular formula of the following compounds and draw their electron-dot structures: (i) Ethane (ii) Ethene (iii) Ethyne
Draw the structure of the following compounds:
1. Butanoic acid
2. Chloropentane
(a) State the reason why carbon can neither form C4+ cations nor C4- anions, but forms covalent bonds. Also state reasons to explain why covalent compounds (i) are bad conductors of electricity (ii) have low melting and boiling points.
(b) Write the structural formula of benzene, C6H6.
What is an oxidising agent? What happens when an oxidising agent is added to propanol? Explain with the help of a chemical equation.
What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds
1. poor conductors of electricity and
2. have low melting and boiling points? What happens when this compound burns in oxygen?
Complete the following chemical equations:
(i)
(ii)
What are esters? How are they prepared? List two uses of esters.
Write the chemical equation to show what happends when sodium hydroxide is added to ethanoic acid?
Compare soaps and detergents on the basis of their composition and cleansing action in hard water.
Name the following compound.
Carry out the following conversions giving complete conditions for the reaction to take place in each case:
1. Ethanoic acid from Ethanol
2. Ethane from Ethene
3. Ester from Ethanoic acid and ethanol
Also state the names given to all the above conversions.
Detergents are preferred over soaps. Why? (Give one reason)

SOLUTIONS:

(a): In an oxygen molecule, both oxygen atoms contribute two electrons each and thus share two electron pairs to form two covalent bonds. As shared pairs are shared by both oxygen atoms, they acquire inert gas configuration of neon atom in valence shell. Such bonds are called double bonds.
(d): (A) is false, but (R) is true. Carbon can neither gain nor lose four electrons to acquire the nearest noble gas configuration. Carbon can share its valence electrons with carbon or other elements.
(a): The given compounds are members of homologous series of alcohol.
(b): When an ester reacts with the base, saponification reaction occurs.
(c)
(d)
(b)
Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat these molecular forces break.
1. (b)
(i) Due to weak intermolecular forces of attraction, carbon compounds generally have low melting and boiling points.
1. Carbon compounds do not contain ions and hence, are generally poor conductors of electricity.
2. Carbon can form only covalent compounds because carbon can neither gain nor lose four electrons to acquire stable octet. The only way by which it can acquire the nearest noble gas configuration is by sharing its valence electrons with other C-atoms or atoms of other elements.
(a) Ethanol (alcohol)
(b) Ethanal (Aldehyde)
(a) General formula of alkyne = CnH(2n-2)
For CxH2, n = 2 and x = 2n-2 ⇒ x=2. For C3Hy, n=3, y=2n-2 = 2*3 - 2 = 4 Hence, x=2, y=4
(b) A is ethyne (C2H2) and B is propyne (C3H4).
(a) Aldehyde (-CHO) group.
1. CH2O
2. Compound (i) is propanal, and compound (ii) is ethanal. They belong to the same homologous series where each successive compound differs from each other by a--CH2 unit.
Other member of same homologous series:
(i) Molecular formula of ethane is C2H6.
1. Molecular formula of ethene is C2H4.
2. Molecular formula of ethyne is C2H2.
(a) Butanoic acid: CH3CH2CH2COOH
(b) Chloropentane: CH3CH2CH2CH2CH2CI
(a) lonic compounds are formed either by gaining or losing electrons from the outermost shells, but carbon which has four electrons in its outermost shell cannot form ionic bonds because
- If carbon forms ionic bonds by gaining four electrons to attain a noble gas configuration then it would be difficult for six protons in the nucleus to hold ten electrons.
- If carbon forms ionic bonds by loss of four electrons then it would require a lot of energy to remove these electrons from outermost shell.
Due to these reasons carbon forms covalent bonds by sharing the valence electrons.
1. Covalent compounds are generally poor conductors of electricity because they do not have free electrons or ions.
2. Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat, these molecular forces break. (b)
The substance that supply oxygen in a reaction for oxidation is called oxidising agent eg. potassium permanganate, potassium dichromate, etc. When propanol is heated with alkaline KMnO4, it gets oxidised to propanoic acid and the purple colour of KMnO4 disappears.
Methane is the first member of alkane series having formula CH4. In this compound the bond formed are covalent bonds.
1. Covalent compounds are generally poor conductors of electricity because they do not have free electrons or ions.
2. Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat, these molecular forces break. When methane is burnt in presence of oxygen then carbon dioxide will be produced.
CH2+O2 -> CO2 + H2O + heat + light
(i) CH3COOC2H5 + NaOH -> CH3COO-Na+ + C2H5OH
Ethyl ethanoate
Sodium ethanoate
Ethanol
1. CH3COOH + NaOH -> CH3COONa + H2O
  Ethanoic sodium sodium acid hydroxide ethanoate
2. C2H5OH + CH3COOH -> CH3COOC2H5 + H2O
ethanol ethanoic ethyl
acid ethanoate
Esters are compounds with functional group COOR and generally volatile liquids having pleasant fruity smell. Esters are prepared when a carboxylic acid reacts with an alcohol in the presence of small amount of concentrated H2SO4 For example, when ethanoic acid reacts with ethanol it forms an ester (i.e. ethyl ethanoate).

Uses of ester:
1. It is used in making perfumes.
2. It is used in making artificial flavours and essences used in ice-creams, sweets and cold drinks.
CH3COOH + NaOH -> CH3COONa + H2O
ethanoic sodium sodium acid hydroxide ethanoate
Soaps and detergents are both cleaning agents with distinct compositions and properties. Here's a comparison between the two based on their composition and cleansing action in hard water:
Composition:
Soaps:
1. Source: Soaps are usually made from natural ingredients such as fats and oils, often derived from plants or animals.
2. Composition: Soaps are salts of fatty acids. They contain a hydrophobic (water-repelling) tail and a hydrophilic (water-attracting) head. The hydrophobic tail binds with grease and oil, while the hydrophilic head allows the soap to dissolve in water.
Detergents:
1. Source: Detergents can be synthetic or derived from petrochemicals.
2. Composition: Detergents are often composed of surfactants, which have a similar structure to soaps. However, detergents can be formulated to be more effective in hard water and have variations in their chemical structures.
Cleansing Action in Hard Water:
Soaps:
Effectiveness in Hard Water: Soaps form insoluble calcium and magnesium salts (soap scum) when used in hard water. This reduces their cleansing effectiveness and can lead to the formation of deposits on clothes and surfaces.
Cleaning Mechanism: Soaps work by emulsifying oils and dirt, allowing them to be dispersed in water. However, the reaction with calcium and magnesium ions in hard water reduces their ability to form a lather and clean effectively.
Detergents:
Effectiveness in Hard Water: Detergents are generally more effective in hard water compared to soaps. Synthetic detergents are designed to be less affected by calcium and magnesium ions, resulting in better cleaning performance in hard water.
Cleaning Mechanism: Detergents work similarly to soaps by breaking down and dispersing oils and dirt. The synthetic nature of detergents allows them to form a lather in hard water and maintain their cleansing action.
The compound is known as ethanal.
(i) Oxidation of ethanol to ethanoic acid:

Here, alkaline KMnO4 or acidified K2Cr2O, dichromate are oxidising agents.
(ii) Addition reaction:

(ii) Esterification:
Detergents work well with hard water and are biodegradable.

Life Processes

Control and Coordination

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

In a neuron, conversion of electrical signal to a chemical signal occurs at/in
1. cell body
2. axonal end
3. dendritic end
4. axon
Which part of the human brain controls body temperature?
1. Pituitary
2. Diencephalon
3. Hypothalamus
4. None of these
Posture and balance of the body is controlled by
1. cerebrum
2. cerebellum
3. medulla
4. pons
The main function of abscisic acid in plants is to
1. increase the length of cells
2. promote cell division
3. inhibit growth
4. promote growth of stem
Iodine is necessary for the synthesis of which hormone?
1. Adrenaline
2. Thyroxine
3. Auxin
4. Insulin
Female sex hormone is termed as
1. androgen
2. insulin
3. oestrogen
4. None of these
Which of the following shows correct reflex arc?
1. Sensory organ→ Spinal cord→ Effector organ
2. Sensory organ→→ Brain→ Effector organ
3. Effector organ→ Brain→ Sensory organ
4. Effector organ→ Spinal cord→ Sensory organ
Plant hormone responsible for phototropism is
1. gibberellin
2. abscisic acid
3. cytokinin
4. auxin
Hypersecretion of growth hormone causes
1. gigantism
2. dwarfism
3. sterility
4. goitre
Deficiency of which hormone causes diabetes?
1. Insulin
2. Thyroxine
3. Relaxin
4. Oestrogen
  SHORT AND LONG QUESTIONS
Mention the function of adrenaline hormone.
Name the plant hormones which help/promote -
(i) cell division (ii) growth of the stem and roots?
What is the function of thyroxine hormone in our body ?
State the function of: (i) gustatory receptors, and
(ii) olfactory receptors.
What is synapse ? In a neuron cell how is an electrical impulse created and what is the role of synapse in this context ?
Name the hormone secreted by human testes. State its functions.
What are plant hormones? Write two important functions of auxin.
(a) How is brain protected from injury and shock?
(b) Name two main parts of hind brain and state the functions of each.
(a) Draw the structure of neuron and label cell body and axon.
(b) Name the part of neuron:
1. where information is acquired
2. through which information travels as an electrical impulse.
List in tabular form three differences between nervous system and Endocrine system.
List the components of reflex arc in correct sequence. State in brief the role of brain in reflex action.
1. Name the parts labelled A and B in the neuron drawn above.
2. Which part acquires the information in the neuron?
3. Through which part does the information travel?
4. In what form does this information travel?
5. Where is the impulse converted into a chemical signal for onward transmission?
Smita’s father has been advised by a doctor to reduce his sugar intake. Name the disease he is suffering from and name the hormone whose deficiency is? Identify the gland that secretes it and mention the function of this hormone. Explain how the time and amount of secretion of this hormone is regulated in human system.
State the functions of plant hormones. Name four different types of plant hormones.
Which part of the brain controls involuntary actions? Write the function of any two regions of it.

SOLUTIONS:

(b) At the axonal end, the electrical impulse releases small amount of chemical substance (i.e. acetylcholine) into the synapse.
(c) Hypothalamus controls and regulates temperature of body, urge of eating, drinking, sleeping, etc.
(b) Cerebellum controls the voluntary actions, e.g. posture.
(c) The main function of abscisic acid in plants is to inhibit growth.
(b) lodine is necessary for the synthesis of thyroxine hormone.
(c) Oestrogen is a female sex hormone.
(a)
(d)
(a)
(a)
Adrenaline hormone is released into the blood from the adrenal gland during stimulation of the nervous system on seeing any adverse situation of fight or fright, it increases the blood pressure, it increases heart beat rate, it increases breathing rate and it diverts blood to essential organs including the heart, brain and skeletal muscles by dilating their blood vessels and constricting those of less essential organs, such as the skin and digestive system.
The plant hormones which help or promote:
(i) Cell division — Cytokinins
ii) Growth of the stem — Gibberellins
Thyroxine hormone regulates the carbohydrate, protein and fat metabolism in the body so as to provide the best growth balance.
(i) Gustatory receptors – these are sensitive to taste
(ii) Olfactory receptors – these are sensitive to smell.
A synapse is the gap between the two neurons. Here the axon terminal of one neuron is in close proximity to the dendrite of the second neuron. When a nerve impulse reaches the knob like nerve ending of an axon, a tiny amount of a chemical substance is released in the synapse. This chemical substance is called as the neurotransmitter. At synapse the electrical signals converted into chemicals, that can easily cross over the gap and pass on to the next neurons where it again converted into electrical signals.
Testes secrete male sex hormone called testosterone. The function of testosterone is to regulate male accessory sex organs and secondary sexual characters like moustache, beard and voice.
Plant hormones can be defined as a chemical substance which is produced naturally in plants and are capable of translocation and regulating one or more physiological processes when present in low concentration.
Two important functions of auxin are that it promotes cell elongation, root formation, cell division, etc.
(a) Brain is covered by a three layered membrane called meninges. In between the layers of meninges and brain, cavity fluid named Cerebro Spinal Fluid (CSF) is filled. The hard skull covers the meninges. Thus Meninges, CSF and Skull protects our brain for a certain extent.
(b) Two main parts of hind-brain are — Medulla and Cerebellum. Their functions are:
Medulla : Involuntary actions such as blood pressure, salivation and
vomiting.
Cerebellum : It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
(a) A nerve cell (Neuron)

(b) (i) Dendrite

(ii) Axon 20.

The reflex arc pathway is shown in the flow chart as follows:
The Reflex arc does not involve brain. It minimises the overloading of brain.
(a) (i) A – Dendrite, B – Axon
1. The information in the neuron is acquired at the end of the dendrite tip.
2. The information travels from the dendrite to the cell body and then along the axon to its end.
3. The information travels in the form of an impulse.
4. The impulse is converted into a chemical signal at the end of the axon.
He is suffering from diabetes. Deficiency of insulin causes diabetes. Pancreas secretes insulin. Insulin helps in regulating blood sugar.
When the sugar level in blood increases, it is detected by the a-cells of the pancreas which responds by producing more insulin. As the blood sugar level falls, insulin secretion is reduced.
Plant hormones help to coordinate growth, development and responses in environment. Four different types of plant hormones are – Auxins, Gibberellins, Cytokinins, Ethylene and Abscisic acid.

Auxins control the tropic (growth related) movements of the plants in response to light, gravity, touch etc by increasing the size of cells.
Under the influence of auxins, the plant stem bends towards unidirectional light where as the roots bend away from it.
Gibberellins stimulate stem elongation and leaf expansion. Its application causes stem elongation in small plants such as cabbage. Spraying gibberellins on sugarcane plant increases the stem size and hence the yield.
Cytokinins are produced in regions of the plant body where rapid cell division occur, such as root tips, developing shoot buds, young fruits and seeds. Cytokinins promote growth by stimulating cell division. They also help in production of new leaves and chloroplasts in leaves.
Ethylene causes ripening of the fruits.
Abscisic acid inhibits (i.e., slows down) the growth in different parts of the plant body. It also inhibits germination of seeds. It increases the tolerance of plant to different kinds of stresses such as temperature changes. So, it is also called the stress hormone in plants. It also causes the drying and falling of older leaves, flowers and fruits.
Hind-brain controls the involuntary actions. Cerebellum controls the coordination of body movement and posture. Medulla oblongata regulates center for swallowing, coughing, sneezing and vomiting.

How Do Organisms Reproduce

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

Assertion (A): Amoeba always produces two daughter amoebae while Plasmodium divides into many daughter cells.
Reason (R): Amoeba undergoes binary fission while Plasmodium undergoes multiple fission.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
The stamen contains
1. stigma
2. pollen grain
3. sepal
4. ovule
Seeds are called products of sexual reproduction because they
1. give rise to new plants
2. are formed by fusion of gametes
3. are formed by the fusion of pollen tubes
4. can survive for a longer period.
Assertion (A): Sexual reproduction involves two parents of different sexes, a male and female, which produce male and female gametes respectively.
Reason (R): The male and female gametes fuse to form a zygot sexual reproduction, which develops into a new individual.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Which one of the following is not a part of the human female reproductive system?
1. Ovary
2. Oviduct
3. Uterus
4. Seminal vesicle
Assertion (A): Testes are located outside the abdominal cavity in the scrotum.
Reason (R): Because sperm formation requires lower temperature than the normal body temperature.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Which of the following techniques is used as a contraceptive method in males only?
1. Copper-T
2. Oral pills
3. Blockage of fallopian tube
4. Blockage of vas deferens
  
  SHORT AND LONG QUESTIONS
Differentiate between ‘self-pollination’ and ‘cross-pollination’. Describe
double fertilisation in plants.
What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
(a) In the human body what is the role of
(i) seminal vesicles, and (ii) prostate gland?
(b) List two functions performed by testis in human beings.
Illustrate the following with the help of suitable diagrams:
1. Binary Fission in Amoeba.
2. Leaf of Bryophyllum with buds.
Illustrate the following with the help of suitable diagrams:
(i) Spore formation in Rhizopus. (ii)Multiple fission in Plasmodium.
(a) Name the parts labelled A, B, C, D and E.

(b) Where do the following functions occur?
1. Production of an egg
2. Fertilisation
3. Implantation of zygote.
(c) What happens to the lining of uterus:
1. before release of a fertilised egg?
2. if no fertilisation occurs?
(a) Draw a diagram showing germination of pollen on stigma of a flower.
1. Label pollen grain, male germ- cells, pollen tube and female germ- cell in the above diagram.
2. How is zygote formed?
Mention the mode of reproduction used by (a) Amoeba (b) Planaria.
What is regeneration? State a reason why a more complex organism cannot give rise to new individuals through this method.
Explain the terms: (i) Implantation (ii) Placenta
List any four reasons for vegetative propagation being practised in the growth of some type of plants.
List any three differences between pollination and fertilisation.
Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.
(a) What is fragmentation in organism? Name a multicell-ular organism which reproduces by this method.
(b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.
Describe in brief the role of (i) testis (ii) seminal vesicle, (iii) vas deferens, (iv) ureter and (v) prostate gland in human male reproductive system.
“DNA copies generated during reproduction will be similar but may
not be identical to the original.” Justify this statement.
List and explain in brief three methods of contraception.
State in brief the changes that take place in a fertilised egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilised?

SOLUTIONS:

(a): Amoeba reproduce through binary fission and produces two daughter amoebae. Plasmodium reproduces through multiple fission and splits to form many new organisms.
(b): Stamen is male reproductive organ of plant which is made up of anther and filament. The anther produces pollen grains.
(b):Seeds are the products of sexual reproduction because fusion of male and female gametes results into formation of zygote which in turn undergoes meiotic division to form embryo. Embryo further develops within the ovule which becomes a seed.
(b)
(d): Female reproductive system consists of ovaries, oviducts, uterus and vagina. The seminal vesicles are the pair of glands found in male reproductive system.
(a): Sperm formation requires 2-2.5°C lower temperature than the normal internal body temperature, so testes are located outside the abdominal cavity in the scrotum.
(d): In males, blockage of vas deferens is called vasectomy which prevents the sperms to getting into the semen.
DNA copying is not perfectly accurate and the resultant errors are a source of variations in populations of organisms.
(a) The role of seminal vesicles and the prostate gland are as follows:
1. Seminal vesicles produce seminal plasma which is in the form of fluid makes the transport of sperms smooth.
2. Prostate gland secretes prostatic fluid that keeps the sperms alive and helps them to swim vigorously.
  1. Two functions performed by testis in human beings are as follows:
    1. Formation of sperms takes place in testis.
    2. They secrete the hormone testosterone which regulates the formation of sperms and brings changes in appearance of boys at the time of puberty.
(i) Binary Fission in Amoeba

(ii) Leaf of Bryophyllum with buds
(i) Spore formation in Rhizopus

(ii) Multiple fission in Plasmodium
(a) A – Oviduct or Fallopian tube;
B – Ovary;
C – Uterus;
D – Cervix;
E – Vagina.
1. (i) Ovaries; (ii) Fallopian tube; (iii) Lining of the uterus.
2. (i) The lining of uterus becomes.
(ii) The lining of uterus slowly breaks and comes out through the vagina as blood and mucous, if no fertilisation occurs.
(a) and (b)
Mode of reproduction used by
1. Amoeba is Binary fission.
2. Planaria is Regeneration.
Regeneration is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts. More complex organisms cannot give rise to new individuals through regeneration because:
1. their body is highly complicated.
2. there are specific organs to do specific functions.
3. there is a labour division in the body of complex organisms.
4. regeneration is carried out by specialised cells which are not present in complex organisms.
(i) Implantation: The embedding of a fertilised mammalian egg (embryo) into the inner thick wall of the uterus (womb) where it will continue its development is called implantation.
(ii) Placenta: It is a complex double-layered spongy vascular tissue in human female formed by the joint activity of maternal and foetal tissues in the wall of uterus that is meant for attachment, nourishment and waste disposal for the foetus.
(i) Vegetative propagation is a cheaper, easier and more rapid method of propagation in plants than growing plants from their seeds.
1. Better quality of plants can be maintained by this method.
2. It results in propagation of those plants which do not produce viable seeds or produce seeds with prolonged period of dormancy.
3. The plants generated from vegetative means are more uniform and genetically similar to the parent stock.
(a) Fragmentation: Multicellular organisms with simple body organisation such as filamentous algae-Spirogyra breaks up into two or more small pieces or fragments upon maturation. These fragments grow into new individuals.

Fragmentation in Spirogyra

(b) Regeneration: It is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts.
- Small cut or broken parts of the organism body grow or regenerate into separate individuals.
- Planaria can be cut into any number of pieces and each piece grows into a complete organism.
- Regeneration is carried out by specialised cells which proliferate and make large number of cells thus, undergoing changes to become various cell types and tissues.
- The changes taking place in an organised sequence is development.
Regeneration in Planaria
Testis: Testes are oval shaped primary reproductive organs in men. The function of testes is to produce sperms and male sex hormone testosterone. The scrotum provides optimal temperature for the formation of sperms.
Seminal vesicle: Seminal vesicles are a pair of thin walled muscular elongated sac which secrete fluid for nourishment of sperms.
vas deferens: The sperms are carried by a long tube called vas deferens to organs called seminal vesicles where the sperms get nourishment and stored.
Ureter: It is the tube that carries urine from kidney to the urinary bladder. In humans, there are two ureters, one attached to each kidney.
Prostate glands: Prostate glands produce a fluid which is released in the urethra along with secretion of seminal vesicles for nourishment and transportation of sperms.
DNA copies generated will be similar, but may not be identical to the original as some variations are so drastic that new DNA copy cannot work with the cellular apparatus it inherits. Such a newborn cell will simply die. Therefore, there could be many other variations in the DNA copies that would not lead to such a drastic outcome. Thus, the surviving cells are similar but slightly different from each other. This tendency of variation during reproduction is the basis for evolution.
Methods of contraception are:
Use of condom for penis or for vagina as a mechanical barrier for the sperms to reach the egg.
Use of oral pills which change the hormonal balance so that eggs are not released.
Surgical method where either the vas deferens of male is blocked or the fallopian tube of female is blocked.
The egg gets fertilised in the oviduct. The fertilised egg, the zygote gets implanted in the lining of the uterus and starts dividing. The uterus prepares itself every month to receive and nurture the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo.

The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. The development of the child inside the mother’s body takes approximately nine months. On completion of 9 months, the child is born as a result of rhythmic contractions of the muscles in the uterus.

If the egg is not fertilised, the thick and nourishing lining of the uterus breaks and comes out through vagina as blood and mucous.

Heredity and Evolution

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

A cross between pea plant with white flowers (vv) and pea plant with violet flowers (VV) resulted in F2 progeny in which ratio of violet (VV) and white (vv) flowers will be
1. 1:1
2. 2:1
3. 3:1
4. 1:3
Assertion (A): In humans, if gene (B) is responsible for black eyes and gene (b) responsible for brown eyes, then the colour of eyes of the progeny having gene combination Bb, bb or BB will be black only.
Reason (R): The black colour of the eyes is a dominant trait.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
Which one of the given statements is incorrect?
1. DNA has the complete information for a particular characteristic.
2. DNA is the molecule responsible for the inheritance of characters from parents to offsprings.
3. Change in information will produce a different protein.
4. Characteristics will remain the same even if protein changes
Consider the following two statements:
1. The trait that expresses itself in F1 generation.
2. The trait that keeps on passing from one generation to another. The appropriate terms for the statements (i) and (ii) respectively are
  1. Recessive trait: Dominant trait
  2. Dominant trait: Recessive trait
  3. Dominant trait: Inherited trait
  4. Recessive trait: Inherited trait
Assertion (A): Human population show a great deal of variations in traits.
Reason (R): All variations in a species have equal chances of surviving in the environment in which they live.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
Assertion (A): The sex of a child in human beings will be determined by the type of chromosome he/she inherits from the father.
Reason (R): A child who inherits 'X' chromosome from his father would be a girl (XX), while a child who inherits a 'Y' chromosome from the father would be a boy (XY).
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
If a pure tall pea plant is crossed with a pure dwarf pea plant then, what percentage of F1 and F2 generation respectively will be tall?
1. 25%, 25%
2. 50%, 50%
3. 75%,100%
4. 100%, 75%
Assertion (A): Height in pea plants is controlled by efficiency of enzymes and is thus genetically controlled.
Reason (R): Cellular DNA is the information source for making proteins in the cell.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
Assertion (A): A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, he got all violet flowers in first generation.
Reason (R): White colour gene is not passed on to next generation.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
  
  LONG AND SHORT QUESTIONS
Justify the statement "Sex of the children will be determined by what they inherit from their father".
"Sex chromosomes in human males and females are XY and XX respectively. Statistical probability of getting either a male or a female child is 50%. Justify this statement giving reason.
If child inherits X-chromosome from the father what will be his/her gender?
What is a gene?
In a cross between violet flowered plants and white flowered plants, state the characteristics of the plants obtained in the F1 progeny.
If the plants of F1 progeny are self-pollinated, then what would be observed in the plants of F2 progeny?
If 100 plants are produced in F2 progeny, then how many plants will show the recessive trait?
A green stemmed rose plant denoted by GG and a brown stemmed rose plant denoted by gg are allowed to undergo a cross with each other.
1. List your observations regarding:
  1. Colour of stem in their F1 progeny.
  2. Percentage of brown stemmed plants in F2 progeny if plants are self pollinated.
  3. Ratio of GG and Gg in the F2 progeny.
2. Based on the findings of this cross, what conclusion can be drawn?
A cross was made between green-stemmed tomato plants denoted by (GG) and purple-stemmed tomato plants denoted as (gg) to obtain F, progeny.
1. What colour of the stem would you expect in their F, progeny and why?
2. Give the percentage of purple-stemmed plants if F1 plants are allowed to self-pollinate to produce F2 progeny.
3. Write the ratio between GG and gg plants in the F2 progeny.
(a) Why did Mendel carry out an experiment to study inheritance of two traits in garden pea?
1. What were his findings with respect to inheritance of traits in F, and F2 generation?
2. State the ratio obtained in the F2 generation in the above mentioned experiment.
"It is a matter of chance whether a couple will have a male or a female child." Justify this statement by drawing a flow chart.
How did Mendel interpret his result to show that traits may be dominant or recessive? Describe briefly.
A cross was made between pure breeding pea plants, one with round and green seeds and the other with wrinkled and yellow seeds.
1. Write the phenotype of F, progeny. Give reason for your answer.
2. Write the different types of F2 progeny obtained along with their ratio when F, progeny was selfed.
In some families, either rural or urban, females are tortured for giving birth to a female child. They do not seem to understand the scientific reason behind the birth of a boy or a girl. Infact the mother is not responsible for the sex of the child and it has been genetically proved that the sex of a newborn is determined by what the child inherits from the father.
1. State the basis on which the sex of a newborn baby is determined in humans.
2. Why is the pair of sex chromosomes called a mismatched pair in males?
3. How is the original number of chromosomes present in the parents restored in the progeny?
OR
(c) Explain by giving two examples of the organisms in which the sex is not genetically determined.
How do Mendel's experiments show that
1. traits may be dominant or recessive?
2. inheritance of two traits is independent of each other?
(a) Why did Mendel choose garden pea for his experiments? Write two reasons.

(b) List two contrasting visible characters of garden pea Mendel used for his experiment.

SOLUTIONS:

(a):
(d):
(d)
(c)
(c): Variations get accumulated or discarded as combined effect of environmental factors and reproduction process.
(a)
(d)
(a): Cellular DNA is the information source for making proteins in the cell. A section of DNA that gives information for one protein is called the gene for that protein. Height in pea plant is regulated by hormones. Hormone production in turn is controlled by genes which control activity of enzyme.
(a)
Sex of the children will be determined by what they inhert from their father. The sperm of father is hetrogametic i.e. 22+X and 22+Y. The egg of mother is homogametic i.e. 22+X and 22+X. 23rd pair of chromosome called sex chromosomes determines the sex of unborn child. When a sperm (22+X) fuses with egg (22+X ) then a girl is born (44+ XX ) when a sperm. When a sperm (22+Y) fuses with egg (22+X ) then a boy is born (44+XY) . Hence sex of the children is determined by X or Y chromosomes of father.
Human female (XX) produces all gametes (ova) with X-chromosomes, while human male (XY) produces 50% gametes (sperms) with X- chromosome while 50% gametes with Y-chromosome. If sperm having X chromosome fertilises the ovum with X chromosome then a female child will be produced, otherwise a male child will be produced.
Sex of the child (offspring) is determined by the type of sperm that fuses with ovum at the time of fertilisation. Therefore, there is 50% chance of a male child being born and a 50% chance of a female child being born.
If a child inherits X-chromosome from the father then the sex of the child will be female.
A gene is a unit of DNA on a chromosome which governs the synthesis of particular protein that controls specific characteristics (or traits) of an organism.
The plants obtained in F1 progeny will be violet since violet is a dominant trait.
If the plants of F, progeny are self pollinated then the F2 generation will have violet and white flowers in the ratio of 3:1.
Self pollination of F1 generation is shown as follows:
The ratio of progeny produced in F2 generation is 3:1. i.e., 3 violet flowers and 1 white flower. Hence, the number of white flowers will be 1x100/4 = 25. Hence, 25 plants will show the recessive trait.
(a) (i) Colour of stem in F, progeny:

The colour in the F1 progeny is green stemmed as green stem colour is dominant.
1. F1 progeny on self pollination:
  1/4 or 25% of F2 progeny are brown stemmed rose plant.
2. Ratio of GG and Gg in F2 progeny: Genotype of F2 progeny - GG : Gg
1 : 2
(b) This is a monohybrid cross. This shows that out of two contrasting traits only one dominant trait appears in F1 generation and the trait which does not express is recessive. On selfing the F1 plants, both the traits appear in next generation but in a definite proportion.
(a) F1 progeny will have green stemmed tomato plants as green is dominant over purple stemmed tomato plants.
1. If F, plants are self pollinated, then the percentage of purple stemmed plant in F2 progeny will be 25%.
2. Ratio of GG and gg plant in F2 generation will be 1: 1.
(a) Mendel carried out crosses with two traits to see the interaction and basis of inheritance between them. In a dihybrid cross given by Mendel, it was observed that when two pairs of characters were considered each trait expressed independent of the other.
1. To study inheritance of traits in F1 and F2 generation, a cross was made between round yellow and wrinkled green parents.
2. In F1 generation, all plants are with round yellow seeds. But in F2 generation, we find all types of plants: Round yellow, Round green, Wrinkled yellow, Wrinkled green.
F2 generation ratio: Round-yellow = 9; Round-green = 3; Wrinkled-yellow = 3; Wrinkled-green = 1.
Sex is determined at the time of fertilisation when male and female gametes fuse. Male produces two types of gametes, ie., having X or Y chromosome and female produces same type of gametes containing X chromosomes. The sex of the child is determined at the time of fertilisation when male and female gametes fuse to form zygote.
If a sperm (male gamete) carrying X chromosome fertilises an egg or ovum (female gamete) carrying X chromosome, then the offspring will be a girl (female). This is because the offspring will have XX combination of sex chromosomes. If a sperm (male gamete) carrying Y chromosome fertilises an egg or ovum (female gamete) which has X chromosome, then the offspring will be a boy (male). This is because the offspring will have XY combination of sex chromosomes. Therefore, there are 50% chance of a male child and 50% chance of a female child.
Mendel crossed the pea plant for two contrasting characters under consideration. The trait that expressed itself in F1 generation was dominant and the one not expressed in F, generation was recessive. He later selfed the plants of F, generation and observed, both parental traits in a definite proportion in F2 generation. Mendel interpreted his results as the trait that expressed itself in F1 was dominant and the one that reappeared in F2 generation was recessive. It can be demonstrated by the following cross:
(a) The given cross was made between pure breeding pea plants, one with round and green seeds and the other with wrinkled and yellow seeds. Yellow seed colour and round seed shape is dominant over green seed colour and wrinkled seed shape. In F1 generation, dominant traits express itself, whereas recessive traits get suppressed.

Therefore, the phenotype of F, progeny is round and yellow.
(b) The different types of F2 progeny obtained along with their ratio when F1 progeny was selfed could be illustrated by the given cross:

Phenotypic ratio: 9: 3: 3: 1
Round yellow seeds - 9; Round green seeds - 3; Wrinkled yellow seeds - 3: Wrinkled green seeds - 1
Round green and wrinkled yellow seeds were new combinations produced in F2 generation.
(a) Sex of child is determined by what it inherits from the father. A child who inherits X chromosome from her father will be a girl and one who inherits a Y chromosome from father will be a boy.
(b) Human beings have 22 pairs of autosomes and one pair of sex chromosomes. The females possess two homomorphic sex chromosomes, named XX while males contain two heteromorphic sex chromosomes, i.e., XY. The Y chromosome is shorter than X chromosome. Therefore a pair of sex chromosomes in human beings is called mismatched pair in terms of type and size.
(c) Gametes contain half the number of chromosomes of parent. But, when the two gametes (male and female) fuse to form the zygote, the normal diploid condition is restored. Hence, the formation of gametes by meiosis and fusion of male and female gamete help to maintain the number of chromosomes in organism.
OR
(c) Two animals in which sex is not determined genetically are turtle and crocodile. The type of sex in them is determined by environmental factors. In turtles. the temperature of egg incubation has a significant effect on the sex of developing embryos. Males are predominant below 28°C, females above 33°C and equal number of the two sexes between 28-33°C. In crocodiles, high temperature induces maleness and low temperature femaleness.
(a) Mendel first crossed pure-bred tall pea plants with pure-bred dwarf pea plants and found that only tall pea plants were produced in the first generation (F,). He then self crossed the tall pea plants of the F, generation and found that tall plants and dwarf plants were obtained in the second generation or (F) in the ratio of 3:1. Mendel said that the trait of dwarfness of one of the parent pea plant had not been lost, it was suppressed in the first generation to re-emerge in the second generation.
He called the suppressed trait of 'dwarfness' as 'recessive trait' and the expressed trait of 'tallness' as the 'dominant trait. In this way, Mendel's experiments with tall and dwarf pea plants showed that the traits may be dominant or recessive.
Hence, this could be explained by the given cross:

(b) Mendel observed that he had started with two combinations of characteristics in seeds, round-yellow and wrinkled-green, and two new combinations of characteristics had appeared in the F2 generation, round- green and wrinkled-yellow. According to Mendel's second law of inheritance more than one pair of traits are considered in a cross simultaneously, the factors responsible for each pair of trait are distributed independently to the gametes.
The cross given below showing dihybrid cross explains that the inheritance of two traits is independent of each other.
F2 generation: Round-yellow = 9, Round-green=3, Wrinkled-yellow = 3, Wrinkled-green =1
(a) Mendel choose garden pea for his experiments because:
1. Pea plants were easy to grow and it shows some clear contrasting traits like some pea plants are tall whereas others are dwarf.
2. Pea plants are self pollinating and many generation of pea plants can be produced in comparatively less time.

(b) The contrasting characters of garden pea plant studied by Mendel are:

Light, Reflection and Refraction

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

The image of an object placed in front of a concave mirror of focal length 15 cm is of the same size as the object. The distance between the object and its image is
1. 15 cm
2. 30 cm
3. 60 cm
4. zero
The relation R = 2f is valid
1. for concave mirrors but not for convex mirrors
2. for convex mirrors but not for concave mirrors
3. neither for concave mirrors nor for convex mirrors
4. for both concave and convex mirrors
In which of the following is a concave mirror used?
1. A solar cooker
2. A rearview mirror in vehicles
3. A safety mirror in shopping malls
4. In viewing full size image of distant tall buildings
The radius of curvature of a converging mirror is 30 cm. At what distance from mirror should an object be placed to obtain a virtual image?
1. Infinity
2. 30 cm
3. Between 15 cm and 30 cm
4. Between 0 cm and 15 cm
Which of the following statements is not true in reference to the diagram shown above?
1. The image formed is real.
2. The image formed is enlarged.
3. The image is formed at a distance equal to double the focal length.
4. The image formed is inverted.
An object of height 4 cm is kept at a distance of 30 cm from the pole of a diverging mirror. If the focal length of the mirror is 10 cm, the height of the image formed is
a) +3.0 cm
b) +2.5 cm
c) +1.0 cm
d) +0.75 cm
When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. The image is
1. real
2. inverted
3. virtual and inverted
4. virtual and erect
If a lens and a spherical mirror both have a focal length of -15 cm, then it may be concluded that
1. both are concave
2. the lens is concave and the mirror is convex
3. the lens is convex and the mirror is concave
4. oth are convex
A lens has a power of +4.0 D. It is
1. a convex lens of focal length 4 m
2. a concave lens of focal length 4 m
3. a convex lens of focal length 0.25 m
4. a concave lens of focal length 0.25 m
An object is placed in front of a concave lens. For all positions of the object the image formed is always
1. real, diminished and inverted
2. virtual, diminished and erect
3. real, enlarged and erect
4. virtual, erect and enlarged
A ray of light is incident as shown. If A, B and C are three different transparent media, then which among the following options is true for the given diagram?
1. ∠1 > ∠4
2. ∠1 < ∠2
3. ∠3 = ∠2
4. ∠3 > ∠4
The refractive index of medium A is 1.5 and that of medium B is 1.33. If the speed of light in air is 3 x 10^8 m/s, what is the speed of light in medium A and B respectively?
1. 2 x 10^8 m/s and 1.33 x 10^8 m/s
2. 1.33 x 10^8 m/s and 2 x 10^8 m/s
3. 2.25 x 10^8 m/s and 2 x 10^8 m/s
4. 2 x 10^8 m/s and 2.25 x 10^8 m/s
A converging lens forms a three-times magnified image of an object, which can be taken on a screen. If the focal length of the lens is 30 cm, then the distance of the object from the lens is
1. -55 cm
2. -50 cm
3. -45 cm
4. -40 cm
Assertion (A): A concave lens of a very short focal length causes higher divergence than one with a longer focal length.
Reason (R): The power of the lens is directly proportional to its focal length.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
Assertion (A): The SI unit of power of the lens is ‘dioptre’.
Reason (R): The power of a concave lens is positive and that of a convex lens is negative.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.
  
  SHORT AND LONG QUESTIONS
List four properties of the image formed by a plane mirror.
A concave lens has a focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also, calculate the size of the image formed.
Draw a ray diagram to represent the nature, position, and relative size of the image formed by a convex lens for the object placed:
1. at 2F1
2. between F1 and the optical center O of the lens
The refractive index of water is 1.33 and the speed of light in air is 3 x 10^8 m/s. Calculate the speed of light in water.
If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it?
name the point on the lens through which a ray of light passes undeviated.
An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find:
1. the position
2. the magnification
3. the nature of the image formed.
COMPETENCY BASED QUESTIONS
An image formed in a convex mirror is always virtual, erect, and smaller in size whatever the position of the object. However, in a concave mirror, the image may be real or virtual: erect or inverted: smaller or bigger in size than the object. This would depend upon the distance of the object from the mirror.

A Concave mirror is used as reflector in
1. Torches
2. Search lights
3. Head lights of motor vehicles
4. All the above
In street lamps, the reflector used is a
1. Convex mirror
2. Concave mirror
3. Plane mirror
4. None of these
Which of the mirrors has a larger field of view?
1. Convex
2. Concave
3. plane
4. all have the same field of view
  SOLUTIONS:
  1. (d): Given, focal length, f = 15 cm Radius of curvature, R = 30 cm
    As the image size is the same as that of the object size, this condition is only valid when object is placed at C (centre of curvature) which means the distance between object and image is zero.
  2. (d): It is valid for both concave mirrors and convex mirrors.
  3. (a): Concave mirrors are the mirrors best suited in solar cookers because concave mirrors are convergent mirror and they are reflect sunlight towards a single focal point.
  4. (d): Radius of curvature of a converging mirror, R = 30 cm focal length = 30/2 = 15 cm
    Thus, the virtual image can be obtained from the mirror if an object is placed between pole and focus, i.e., between 0 cm and 15 cm.
  5. (b): Image formed is enlarged is not true. When object is placed at C, image formed is real, inverted and of same size as object.
  6. (c) Given, height of object (h) = +4 cm
    Object distance (u) = -30 cm (object placed left side of the mirror) Focal length, f = +10 cm
    
    Mirror formula,
    
    Hence, the height of the image formed is 1 cm.
  7. (d): When an object is placed between the principal focus and pole of a concave mirror, an enlarged virtual and erect image is formed behind the mirror.
  8. (a): As the focal length of a concave mirror and a concave lens is taken as negative, both are concave in nature.
  9. (c): Given, the power of a lens = 4 D
    For convex lens focal length is always positive.
    
    P = 1/f 4 = 1/f
    f = 0.25 m
    Hence, given lens is convex lens of 0.25 m focal length.
  10. (b): The image formed by of a concave lens is always virtual, diminished and erect.
  11. (c): In A, B and C transparent media, ∠1 > ∠2 as light bends towards the normal and ∠3 < ∠4 as light bends away from the normal. ∠3 = ∠2, because of alternate angles between two normals.
  12. (d): Given, the refractive index of medium A, μa = 1.5 Refractive index of medium B, μb = 1.33 Speed of light in air, c = 3 x 10^8 m/s
    μ = Speed of light in vaccum = c Speed of lightin medium v
    Hence, speed of light in medium A is 2 x 10^8 m/s and in medium B is
    2.25 x 10^8 m/s.
  13. (d): Given, converging lens image is three times magnified, focal length, f = 30 cm.
    As we know, when a convex lens forms a magnified and real image, then the image is inverted i.e., magnification must be negative.
    Therefore, magnification, m = -3
    
    Thus, object distance is at -40 cm from the lens.
  14. (c): The concave lens of very short focal length causes a higher divergence than the one with a longer focal length. So, assertion (A) is true. The power of lens is inversely proportional to its focal length. So, Reason
    (R) is false.
  15. (c): The S.I. unit of power of lens is 'Dioptre. So, assertion (A) is true. The power of a concave lens is negative and that of a convex lens is positive. So, reason (R) is false.
  16. Properties of image formed by a plane mirror:
    1. It is always virtual and erect.
    2. Its size is equal to that of the object.
    3. It is formed at the same distance behind the mirror as the object is in front of the mirror.
    4. It is laterally inverted.
  17. f = -20 cm, ho = 5 cm, v = -15 cm
    Image is diminished and virtual
  18. (a) At 2F1
    
    Nature: Real, inverted, size to size Position: At 2F
    
    (b) Between 2F1 and the optical center O of lens
    
    Nature: Virtual, erect, enlarged Position: On the same side of the lens
  20. Concave lens.
  21. Optical centre.
  22. u = – 30 cm, f = 20 cm (a)
    
    Image is formed at a distance of 60 cm from the lens on the right side.
    1. m = v/u = 60/ (-30) = -2
      
      So, the image is inverted and double the size of the object.
    2. Image is real as v>0, inverted and enlarged.
  23. D
  24. A
  25. A

The Human Eye and the Colorful World

Electricity

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

The expressions that relate (i) Q. I and t and (ii) Q. V and W respectively are (Here the symbols have their usual meanings)
1. (i) I = Q/t (ii) W = V/Q
2. (i) Q = I*t (ii) W = V*Q
3. (i) Q = I/t (ii) W = V/Q
4. (i) I = Q/t (ii) Q = V/W
A student plots V-I graphs for three samples of nichrome wire with resistances R1, R2 and R3. Choose from the following the statements that holds true for this graph.
1. R1 = R2 = R3
2. R1 > R2 > R3
3. R3 > R2 > R1
4. R2 > R1 > R3
A cylindrical conductor of length 'T' and uniform area of cross section 'A' has resistance 'R’. The area of cross section of another conductor of same material and same resistance but of length '2l' is
1. A/2
2. 3A/2
3. 2A
4. 3A
Assertion (A): Alloys are commonly used in electrical heating devices like electric iron and heater.
Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constituent metals.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
If a person has five resistors each of value 1/5 ohm, then the maximum resistance he can obtain by connecting them is
1. 1 ohm
2. 5 ohm
3. 10 ohm
4. 25 ohm
Two LED bulbs of 12 W and 6 W are connected in series. If the current through 12 W bulb is 0.06 A the current through 6 W bulb will be
1. 0.04 A
2. 0.06 A
3. 0.08 A
4. 0.12 A
The resistance of a resistor is reduced to half of its initial value. If other parameters of the electrical circuit remain unaltered, the amount of heat produced in the resistor will become
1. four times
2. two times
3. half
4. one fourth
The resistance of a resistor is reduced to half of its initial value. In doing so, if other parameters of the circuit remain unchanged, the heating effects in the resistor will become
1. two times
2. half
3. one-fourth
4. four times
An electric kettle consumes 1 kW of electric power when operated at 220 V. The minimum rating of the fuse wire to be used for it is
1. 1A
2. 2A
3. 4A
4. 5A
Two bulbs of 100 W and 40 W are connected in series. The current through the 100 W bulb is 1 A. The current through the 40 W bulb will be
1. 0.4A
2. 0.6 A
3. 0.8 A
4. 1 A
  
  SHORT AND LONG QUESTIONS
(a) Define the term ‘coulomb’.
(b) State the relationship between the electric current, the charge moving through a conductor and the time of flow.
Calculate the charge passing through an electric bulb in 20 minutes if the value of current is 200 mA.
Study the following electric circuit and find (i) the current flowing in
the circuit and (ii) the potential difference across 10 Ω resistor.
(a) An electric iron of 1 kW is operated at 220 V. Find which of the following fuses that respectively rated at 1 A,3 A and 5 A
can be used in it.
(b) An electrical fuse is rated at 2 A. What is meant by this statement?
Find the current flowing through the following electric circuit.
Two devices of rating 44 W, 220 V and 11 W, 220 V are connected in series. The combination is connected across a 440 V mains. The fuse of which of the two devices is likely to burn when the switch is ON? Justify your answer.
Consider the circuit shown in the diagram. Find the current in 3Ω
resistor.
For the circuit shown in this diagram, calculate
1. the resultant resistance.
2. the total current.
3. the voltage across 7 Ω resistor.
A 9 Ω resistance is cut into three equal parts and connected in parallel. Find the equivalent resistance of the combination.
(a) How is the direction of electric current related to the direction of flow of electrons in a wire?
(b) Calculate the current in a circuit if 500 C of charge passes through it in 10 minutes.
An electric iron has a rating of 750 W, 220 V. Calculate the (i) current flowing through it, and (ii) its resistance when in use.
(a) List the factors on which the resistance of a conductor in the shape of a wire depends.
1. Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason.
2. Why are alloys commonly used in electrical heating devices? Give reason.
Study the following electric circuit in which the resistors are arranged in three arms A, B and C:
1. Find the equivalent resistance of arm A.
2. Calculate the equivalent resistance of the parallel combination of the arms B and C.
3. (i) Determine the current that flows through the ammeter.
OR
(ii) Determine the current that flows in the ammeter when the arm B is withdrawn from the circuit.
(a) List two disadvantages of using a series circuit in homes.
(b) Calculate the effective resistance between A and B in the circuit given below:
(i) State Joule's law of heating. Express it mathematically when an appliance of resistance R is connected to a source of voltage V and the current / flows through the appliance for a time t.
(ii) A 52 resistor is connected across a battery of 6 volts. Calculate the energy that dissipates as heat in 10 s.
Compare the power used in 2 ohm resistor in each of the following circuits.

SOLUTIONS:

(b): As, I=Q/t , V=W/Q or Q=It, W=VQ
(d): The inverse of the slope of I-V graph gives the resistance of the material. Here the slope of R3 is highest. Thus, R2>R1>R3.
(c): The resistance of a conductor of length I, and area of cross section, A is
(c): Alloy : These are mixture of metal with other elements in nature.
(a): The maximum resistance can be obtained from a group of resistors by connecting them in series. Thus, Rs = 1/5 + 1/5 + 1/5 + 1/5 + 1/5 = 1 ohm
(b): As they are connected in series, so current is same in both the bulbs.
(b): As voltage is same, resistance is halved,
(a): We know,
(d): Given: P = 1kW and V = 220 V P = VI
I = P/V = 4.54 A
So, minimum rating of fuse wire is 5 A.
(d) : Given power of first bulb = 100 W and second buld P2 = 40 W.
Current through 100 W bulb, I1 = 1 A Current through 40 W bulb, l2 =?
Since both the bulbs are connected in series, the electric current passing through both the bulbs are same i.e., I2 = 1 A.
(a) When 1 A current flows across the wire in 1 second, the charge transfer across its ends is said to be 1 coulomb.
(b) The relationship between the electric current I, the charge q and time t is: I = q/t
t = 20 * 60 = 1200 s I = 200 mA = 0.2 A
Charge passing = q = It = 240 C
10 ohm and 20 ohm are connected in series, their eq. resistance is
Rs = R1 + R2 = 30 ohm
1. Current flowing in the circuit
  I = V/Rs = 3/30 = 0.1 A
2. Potential difference across 10 ohm resistor
  V = IR = 0.1 * 10 = 1 V
(a) Given: P = 1 kW = 1000 W and V = 220 V
Current drawn, I = P/V = 4.54 A
To run iron of 1 kW, rated fuse of 5 A should be used.
(b) It means, the maximum current will flow through it is only 2 A. Fuse wire will melt if the current exceeds 2 A value through it.
Series combination of 1 ohm, 2 ohm and 3 ohm resistance is in parallel combination with 6 ohm. Their equivalent resistance is

Now, 3.6 ohm, 2.4 ohm and 3 ohm are in series, their equivalent resistance be

Hence, the current flowing through the circuit is:
I = V/R = 4.5/9 = 0.5 A
3 Ω and 6 Ω are in parallel.
1/ Rp = 1/3 + 1/6 = 1/2 ohm Rp = 2 ohm
Rp and 10 Ω are connected in series. So, Rs = Rp + 10 Ω = 12 Ω

Total current in circuit, I = V/Rs = 12/12 = 1 A Potential difference across Rp = I*Rp = 2 V So, Potential difference across 3 ohm = 2 V

Current throught 3 ohm, I1 = V/R1 = 2/3 = 0.67 A
(b)
Resistance of each part = R/3 = 3 ohm
R1 = R2 = R3 = 3 ohm
In parallel combination,
1/ Rp = 1/R1 + 1/R2 + 1/R3 = 1 ohm
(a) Conventional direction of electric current is opposite to the direction of flow of electrons in a wire.
(b) q = 500 C, t = 10 X 60 = 600 s. I = 500/600 = 5/6A
Given: P = 750 W, V = 220 V
1. P = VI
  750 = 220 * I
  I = 750/220 = 3.40 A
2. P = V2/R
  R = 220*220/750 = 64.53 ohm
(a) Resistance of a conductor depends upon the following factors:
1. Length of the conductor: Greater the length (l) of the conductor more will be the resistance (R).
2. Area of cross-section of the conductor: Greater the cross-sectional area of the conductor, less will be the resistance.
3. Nature of conductor
  1. Metal have very low resistivity and hence they are good conductors of electricity. Whereas glass has very high resistivity so glass is a bad conductor of electricity.
  2. Alloys are commonly used in electrical heating devices due to the following reasons
1. Alloys have higher resistivity than metals
2. Alloys do not get oxidised or burn readily.
(a) Two disadvantages of using a series circuit in homes:
1. If all devices are connected in series, the greater's the resistance.
2. If a device have faulted then all devices of home stop working.
  (b) Equivalent resistance between A and B
  
  We know that 6 ohm and 4 ohm are in series, then
  R1 =6+4 = 10 ohm
  and 3 ohm and 3 ohm are in series, R3 = 3 +3 = 6 ohm Now equivalent resistance between A and B,
  1/ Rab = 1/10 + 1/15 + 1/6 = 1 / 3 Rab = 3 ohm
(i) According to the Joule's law of heating, when a current (I) is passed through a conductor of resistance (R) for a certain time (t), the conductor gets heated up and the amount of energy released is given by
H = I2Rt or V2t/R
(ii) Here, V = 6 volt, R=5 ohm, t = 10 sec H = 6*6*10/5
H = 72 J
In circuit A,

Total resistance, R = 1+2 =3 ohm

Voltage across 2 ohm = Vtotal/Rtotal * 2 = 6/3 * 2 = 4 V Power used in 2 ohm resistor, P = V2/R = 8 W

In circuit B, Voltage across both the resistance is same i.e. 4V and both are connected in parallel combination.

Power used in 2 ohm resistor = V2/R = 4*4/2 = 8 W

:. Power used in 2 ohm resistor in each case is same i.e. 8 W.

Magnetic Effects of Electricity Current

TOP 25 QUESTIONS

MULTIPLE CHOICE QUESTIONS

Assertion (A): The magnetic field lines around a current carrying straight wire do not intersect each other.
Reason (R): The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.
1. Both (A) and (R) are true and (R) is the correct explanation of the (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true, but (R) is False.
4. (A) is false, but (R) is true.
The correct pattern of magnetic field lines of the field produced by a current-carrying circular loop is
a)

b)

c)

d)
An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is
1. towards right
2. towards left
3. into the page
4. out of the page
A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of the magnetic field will be north to south at a point
1. directly above the wire
2. directly below the wire
3. located in the plane of the paper on the north side of the wire
4. located in the plane of the paper on the south side of the wire
Assertion: A current carrying straight conductor experiences a force when placed perpendicular to the direction of magnetic field.
Reason: The net charge on a current carrying conductor is always zero.
1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.
  
  Hans Christian Oersted (1777-1851) observed that a compass needle suffers a deflection when placed near a metal wire carrying an electric current. This discovery gave the first evidence of a connection between electric and magnetic phenomena. Andre Ampere (1775-1836) grasped the significance of Oersted's discovery. He carried out a large series of experiments to explore the relationship between current electricity and magnetism. On the basis of experiments, he hypothesised that all magnetic phenomena are due to circulated electric currents.
  Later on many devices such as electromagnets, electric motors, microphones, electric generators, etc. were developed on the basis of magnetic phenomena.
A magnetic needle is a/an :
1. isolated north pole pivoted at its centre of mass.
2. isolated south pole pivoted at its centre of mass.
3. ordinary needle made of soft iron and pivoted at its centre of mass.
4. small bar magnet pivoted at its centre of mass.
A freely suspended magnet always rests in geographically north and south direction because:
1. the Earth has two poles.
2. the Earth behaves as a huge magnet.
3. the magnetic north pole of the Earth's magnet is located very close to its south pole.
4. the magnetic south pole of the Earth's magnet is located very close to its south pole.
When a current flows through a straight conductor, a magnetic field is produced around it. Consider the following statements about this field:
1. The direction of the magnetic field of a current carrying straight conductor is determined by right-hand thumb rule.
2. A charged body placed in this field experiences a force whose direction is given by Fleming's left- hand rule.
3. The magnetic field lines around a current carrying straight conductor are in the form of concentric circles with the conductor as the centre.
  The correct statement(s) is/are:
  1. I only
  2. Ill only
  3. I and II
  4. I and III
The strength of magnetic field of a current carrying solenoid is
1. minimum at its ends
2. uniform inside it at all points
3. maximum at its centre
4. zero at its centre
Which one of the following particles would not experience a force while moving perpendicular to a uniform magnetic field?
1. A neutron
2. An alpha particle
3. An electron
4. A proton
  
  SHORT AND LONG QUESTIONS
Why do two magnetic field lines not intersect each other?
Draw magnetic field lines around a bar magnet. Name the device which is used to draw magnetic field lines.
Study the diagram given below and answer the questions that follow:
1. Why do the iron filings arrange in such a pattern?
2. What does this pattern demonstrate?
3. Why do the iron filings near the bar magnet seem to align in the shape of closed curves?
A compass needle is placed near a current carrying straight conductor. State your observation for the following cases and give reasons for the same in each case.
1. Magnitude of electric current is increased.
2. The compass needle is displaced away from the conductor.
State Right Hand Thumb rule to find the direction of the magnetic field around a current carrying straight conductor.
How will the magnetic field be affected on:
1. increasing the current through the conductor
2. reversing the direction of flow of current in the conductor?
Draw the pattern of magnetic field lines of the magnetic field produced by a solenoid through which a steady current flows.
Give reason for the following
1. There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid.
2. The current carrying solenoid when suspended freely rests along a particular direction.
A current carrying conductor is placed in a magnetic field. Now answer the following.
1. List the factors on which the magnitude of force experienced by conductor depends.
2. When is the magnitude of this force maximum?
3. State the rule which helps in finding the direction of motion of conductor.
Give reason for the following:
The burnt out fuse should be replaced by another fuse of identical rating.
Give reasons for the following:
It is dangerous to touch the live wire of the main supply rather than neutral wire.
Give reasons for the following:
Using fuse in a household electric circuit is important.
Name two safety measures commonly used in an electric circuit and appliances.
Draw a schematic diagram of a common domestic circuit showing provision of
1. Earth wire
2. Main fuse
3. Electricity meter
4. Distribution box
Distinguish between short circuiting and overloading.

SOLUTIONS:

(b): Assertion is true and reason is also true, but reason is not the correct explanation of assertion. Magnetic field lines around a current carrying straight wire do not intersect each other because at the point of intersection there will be two directions which is not possible. Also, the strength of magnetic field increased by increasing the magnitude of the current in the wire.
(c): By the use of Maxwell's Right hand rule, the correct field lines are shown by option (c).
(d): According to the Fleming's left hand rule, the direction of force is out of the page.
(a): According to right hand thumb rule, the point is at the direction above the wire.
(b): Magnetic force, F = qvBsinO . In current carrying wire, net charge is zero because of equal number of electrons and protons present in the wire, but only electrons are moving.
(d): A magnetic needle is a small bar magnet pivoted at its center of mass.
(d): A freely suspended magnet always rest in north- south direction because the north-pole of the magnet lies in the geographic north direction and the south pole of the magnet lies in the geographic south direction.
(d): Right hand thumb rule says that straight thumb of right hand points in the direction of electric current and direction of curled finger represents the direction of magnetic flied in a straight conductor. Flemming left hand rule gives direction of force experienced by current carrying conductor in magnetic field. The magnetic field due to straight conductor is in the form of concentric magnetic lines.
(b): The strength of magnetic field of a current carrying solenoid is uniform inside it at all points.
(a): Neutron does not experience force while moving perpendicular in uniform magnetic field as neutron has no charge.
The direction of magnetic field (B) at any point is obtained by drawing a tangent to the magnetic field line at that point. In case, two magnetic field lines intersect each other at the point P as shown in figure, magnetic
field at P will have two directions, shown by two arrows, one drawn to each magnetic field line at P, which is not possible.
Compass needle is used to draw magnetic field lines.
(a) The lines along which the iron filings align themselves represent the magnetic field lines of the bar- magnet.
1. This pattern of iron filings demonstrate that the magnet exerts its influence in the region surrounding it. Therefore, the iron filings experience a force.
2. It is taken by convention that the field lines emerges from north pole and merge at the south pole. Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus, the magnetic field lines are closed curves.
(a) As the amount of magnetic field strength is directly proportional to the amount of current, so the deflection of compass needle
increases.
1. Since magnetic field strength at a point is inversely proportional to the distance from the wire. Hence deflection of compass decreases when it is displaced away from the conductor.
It states that you are holding a current carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your finger will wrap around the conductor in the direction of the field lines of the magnetic field.

16.(i) If the current is increased, the magnetic field strength also increases.

(ii) If the direction of current is reversed, the direction of magnetic field also get reversed.

17.

(i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid because it behaves similar to that of a bar magnet and has a magnetic field line pattern similar to that of a bar magnet. Thus the ends of the straight solenoid behaves like poles of the magnet, where the converging end is the south pole and the diverging end is the north pole.
(ii) The current carrying solenoid behaves similar to that of a bar magnet and when freely suspended aligns itself in the north-south direction.
(i) When a current carrying wire is placed in a magnetic field, it experiences a magnetic force that depends on
1. current flowing in the conductor
2. strength of magnetic field
3. length of the conductor
4. angle between the element of length and the magnetic field.
  1. Force experienced by a current carrying conductor placed in a magnetic field is largest when the direction of current is perpendicular to the direction of magnetic field.
  2. The rule used in finding the direction of motion of the conductor placed in a magnetic field is Fleming's left hand rule.
  Fleming's left hand rule is as follows:
  Stretch out the thumb, the forefinger, and the second (middle) finger of the left hand so that these are at right angles to each other. If the forefinger gives the direction of the magnetic field (N to S), the second (middle) finger gives the direction of current then the thumb gives the direction of the force acting on the conductor.
A burnt out fuse should be replaced with identical rating because it helps in protecting the circuit from overloading and short circuiting. If a fuse of higher rating is used then it may not melt and cut off the supply during overloading. Similarly a fuse of lower rating may melt frequently even for a normal flow of current. This results in decreasing the efficiency of the circuit.
Live wire is at 220 V and neutral wire is at zero volt since the electric current flows from higher potential to lower potential, we can get an electric shock by touching live wire but that is not the case with neutral wire.
Fuse is an important safety device. It is used in series with any electrical appliance and protects it from short- circuiting and overloading.
Fuse and the connection of earthing wire are the two safety measure commonly used in electric circuit and appliances.
Diagram of domestic electric wiring from electric pole to a room
Overloading: The condition in which a high current flows through the circuit and at the same time too many appliances are switched on then the total current drawn through the circuit may exceed its rated value.

Short circuiting: The condition when the live wire comes in direct contact with the neutral wire, due to which a high current flows in the circuit.

a) (i) Amylase	(ii) Pepsin	(iii) Bile
b) (i) Amylase	(ii) Bile	(iii) Trypsin
c) (i) Lipase	(ii) Amylase	(iii) Pepsin
d) (i) Trypsin	(ii) Bile	(iii) Amylase

Zn(s) +	2NaOH(aq)	--------------> Na2ZnO2(aq)	+	H2(g)
Zinc	sodium	sodium		hydrogen
	hydroxide	zincate		gas

sodium	hydrochloric	sodium	water
hydroxide	acid	chloride

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Metals and Non Metals

TOP 25 QUESTIONS

Opening and closing of stomata is due to

Assertion (A): The inner walls of the small intestine have finger-like projections called villi which are rich in blood.

Reason (R): These villi have a large surface area to help the small intestine in completing the digestion of food.

In human alimentary canal, the specific enzyme/juice secreted in locations (i), (ii) and (iii) are

The length of the small intestine in a deer is more as compared to the length of the small intestine of a tiger. The reason for this is

The sequence of anaerobic respiration in our muscle cells during heavy exercise is

Assertion (A): The rate of breathing in aquatic organisms is much slower than that seen in terrestrial organisms.

Reason (R): The amount of oxygen dissolved in water is very low as compared to the amount of oxygen in air.

The function of the lining of mucus in the nasal passage of human beings is to

In living organisms during respiration which of the following products are not formed if oxygen is not available?

Assertion (A): The walls of the atria are thicker than those of theventricles.

Reason (R) Ventricles have to pump blood into various organs at high pressure.

The separation of the right side and the left side of the heart is useful to

Upward movement of water in tall trees is due to

Consider the following statements in connection with the functions of the blood vessels marked A and B in the diagram of a human heart as shown.

Blood vessel A - It carries carbon dioxide rich blood to the lungs.

Blood vessel B - It carries oxygen rich blood from the lungs.

Blood vessel B - Left atrium relaxes as it receives blood from this blood vessel.

Blood vessel A- Right atrium has thick muscular wall as it has to pump blood to this blood vessel.

The correct statements are:

In the given diagram A, B, C and D respectively are

Which one among the following is not removed as a waste product from the body of a plant?

Which one of the following statements is correct about the human circulatory system?

Explain the process of nutrition in Amoeba.

How are the alveoli designed to maximize the exchange of gases?

(i) Write the balanced chemical equation for the process of photosynthesis,

(ii) When do the desert plants take up carbon dioxide and perform photosynthesis?

Why are the walls of ventricles thicker than the auricles?

State the role of the following in the human digestive system :

(i) Digestive enzymes (ii) Hydrochloric acid (iii) Villi

Draw a diagram of the human respiratory system and label it :

(i) Diaphragm (ii) Larynx

(a) Name the site of exchange of material between the blood and surrounding cells.

(b) Draw a schematic representation of transport and exchange of oxygen and carbon dioxide in human body.

Control and Coordination

Heredity and Evolution

Light, Reflection and Refraction

TOP 15 QUESTIONS

Person suffering from cataract has

In the diagram given below, X and Y are the end colours of the spectrum of white light. The colour of 'Y' represents the

Which one of the following is the correct reason for twinkling of stars?

Which of the following statement is not true for scattering of light?

Rainbow is a natural spectrum. It is produced because of:

In the given diagram showing refraction of a narrow beam of a monochromatic light through a glass prism, the angles marked 1 and 2 respectively are:

Blue colour of clear sky is due to:

The sky appears dark to passengers flying at very high altitudes mainly because

Observe the following diagram and answer the questions following it:

Identify the defect of vision shown.

List its two causes.

Name the type of lens used for the correction of this defect.

Observe the following diagram showing an image formation in an eye:

Identify the defect of vision shown in the figure.

List its two causes and suggest a suitable corrective lens to overcome this defect.

A student uses spectacles of focal length - 2.5 m.

Name the defect of vision he is suffering from.

Which lens is used for the correction of this defect?

List two main causes of developing this defect.

Compute the power of this lens.

A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m.

List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain.

Why the student is unable to see distinctly the objects placed beyond 5 m from his eyes?

The type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens?

If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention.

The colour of clear sky from the earth appears blue but from the space it appears black. Why?

Give reasons:

Red colour is selected for danger signals.

The sky appears dark in space.

The time difference between actual sunset and apparent sunset is about 2 minutes.

Why is Tyndall effect shown by colloidal particles? State four instance of observing the Tyndall effect.

Electricity

Our Environment