Solutions-NCERT Exemplar Problems & Solution

MCQs

Question: 1 – Which of the following units is useful in relating concentration of solution with its vapour pressure?

1. Mole fraction
2. Parts per million
3. Mass percentage
4. Molality

Answer: (i) Mole fraction

Question: 2 – On dissolving sugar in water at room temperature, solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid?

1. Sugar crystals in cold water
2. Sugar crystals in hot water
3. Powdered sugar in cold water
4. Powered sugar in hot water

Answer: (iv) Powdered sugar in hot water

Explanation: Since, after dissolving of sugar in water, solution becomes cool when touched, this means dissolution is endothermic. That is at high temperature dissolution will be rapid.

Thus, powdered sugar having large surface area, and will be dissolved faster in hot water.

Question: 3 – At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is _ _ _ _.

1. Less than the rate of crystallisation
2. Greater than the rate of crystallization
3. Equal to the rate of crystallisaion
4. Zero

Answer: (iii) Equal to the rate of crystallisaion

Explanation: Since, at equilibrium, rate of dissolution = rate of crystallization

Question: 4 – A beaker contains a solution of substance ‘A’. Preparation of substance ‘A’ takes place when small amount of ‘A’ is added to the solution. The solution is _ _ _ _ _ .

1. Saturated
2. Supersaturated
3. Unsaturated
4. Concentrated

Answer: (ii) Supersaturated

Explanation: When solution is saturated, no more substance can be dissolved it. But in supersaturated solution, when even a small amount of substance is added, precipitation of substance started.

Question: 5 – Maximum amount of a solid solute that can be dissolved in a specific amount of a given liquid solvent does not depend upon _ _ _ _ _ .

1. Temperature
2. Nature of solute
3. Pressure
4. Nature of solvent

Answer: (iii) Pressure

Question: 6 – Low concentration of oxygen in the blood and tissue of people living at high altitude is due to _ _ _ _ .

1. low temperature
2. low atmospheric pressure
3. high atmospheric pressure
4. both low temperature and high atmospheric pressure

Answer: (ii) low atmospheric pressure

Question: 7 – Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s Law?

1. Methanol and acetone
2. Chloroform and acetone
3. Nitric acid and water
4. Phenol and aniline

Answer: (i) Methanol and acetone

Explantion: When acetone is added into methanol, the molecules of acetone get in between the molecules of methanol and break the strength of hydrogen bond present in methanol.

Question: 8 – Colligative properties depends on _ _ _ _ .

1. The nature of the solute particles dissolved in solution
2. The number of solute particles in solution
3. The physical properties of the solute particles dissolved in solution
4. The nature of solvent particles

Answer: (ii) The number of solute particles in solution

Question: 9 – Which of the following aqueous solutions should have the highest boiling point?

1. 1.0 M NaOH
2. 10 M Na₂SO₄
3. 1.0 NH₄NO₃
4. 1.0 M KNO₃

Answer: (ii) 10 M Na₂SO₄

Question: 10 – The unit of ebullioscopic constant is _ _ _ _ _ .

Question: 11 – In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl₂ solution is _ _ _ _ _ .

1. The same
2. About twice
3. About three times
4. About six times

Answer: (iii) About three times

Question: 12 – An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because _ _ _ _ _ .

1. It gains water due to osmosis
2. It loses water due to reverse osmosis
3. It gains water due to reverse osmosis
4. It loses water due to osmosis

Answer: (iv) It loses water due to osmosis

Question: 13 – A t a given temperature, osmotic pressure of a concentrated solution of a substance _ _ _ _ _ .

1. Is higher than that at a dilute solution
2. Is lower than that of a dilute solution
3. Is same as that of a dilute solution
4. Can not be compared with osmotic pressure of dilute solution

Answer: (i) Is higher than that at a dilute solution

Question: 14 – Which of the following statements is false?

1. Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.
2. The osmotic pressure of a solution is given by the equation π = CRT (Where C is the molarity constant)
3. Decreasing order of osmotic pressure for 0.01 M aqueous solutions of barium chloride, potassium chloride, acetic acid and sucrose is BaCl₂ > KCI > CH₃COOH > Sucrose
4. According to Raoult’s Law, the vapour pressure exerted by a volatile component of a solution is directly proportional to its mole fraction in the solution

Answer: (i) Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.

Question: 15 – The values of van’t Hoff factors for KCl, NaCl and K₂SO₄, respective are _ _ _ .

1. 2, 2 and 2
2. 2, 2 and 3
3. 1, 1 and 2
4. 1, 1 and 1

Answer: (ii) 2, 2 and 3

Question: 16 – Which of the following statements is false?

1. Units of atmospheric pressure and osmotic pressure are the same
2. In reverse osmosis, solvent molecules move through a semi-permeable membrane from a region of lower concentration of solute to a region of higher concentration
3. The value of molal depression constant depends on nature of solvent
4. Relative lowering of vapour pressure, is a dimensionless quantity

Answer: (ii) In reverse osmosis, solvent molecules move through a semi-permeable membrane from a region of lower concentration of solute to a region of higher concentration

Question: 17 – Value of Henry’s constant KH is _ _ _ _.

1. Increases with increase in temperature
2. Decreases with increase in temperature
3. Remains constant
4. First increases, then decreases

Answer: (i) Increases with increase in temperature

Question: 18 – The value of Henry’s constant KH is _ _ _ _.

1. Greater for gases with higher solubility
2. Greater for gases with lower solubility
3. Constant for all gases
4. Not related to the solubility of gases

Answer: (ii) Greater for gases with lower solubility

Question: 19 – Consider the figure and mark the correct option.

1. Water will move from side (A) to side (B) if a pressure lower than osmotic pressure is applied on piston (B)
2. Water will move from side (B) to side (A) if a pressure greater than osmotic pressure is allied on piston (B)
3. Water will move from side (B) to side (A) if a pressure equal to osmotic pressure is applied on piston (B)
4. Water will move from side (A) to side (B) if pressure equal to osmotic pressure is applied on piston (A)

Answer: (ii) Water will move from side (B) to side (A) if a pressure greater than osmotic pressure is allied on piston (B)

Question: 20 – We have three aqueous solutions of NaCl lavelled as ‘A’, ‘B’ and ‘C’ with concentrations 0.1M, 0.01M and 0.001M, respectively. The value of van’t Hoff factor for these solutions will be in the order _ _ _ _ .

1. i_A < i_B < i_C
2. i_A > i_B > i_C
3. i_A = i_B = i_C
4. i_A < i_B > i_C

Answer: (i) i_A < i_B < i_C

Question: 21 – On the basis of information given below mark the correct option.

Information:

1. In bromoehtane and chloroethane mixture, intermolecular interactions of A – A and B – B type are nearly same as A – B type interactions.
2. In ethanol and acetone mixture, A – A or B – B type intermolecular interactions are stronger than A – B type interactions.
3. In chloroform and acetone mixture, A – A or B – B type intermolecular interactions are weaker than A – B type interactions

1. Solution (B) and (C) will follow Raoult’s Law
2. Solution (A) will follow Raoult’s Law
3. Solution (B) will show negative deviation from Raoult’s Law
4. Solution (C) will show positive deviation from Raoult’s Law

Answer: (ii) Solution (A) will follow Raoult’s Law

Question: 22 – Two beakers of capacity 500 mL were taken. One of these beakers, labeled as ‘’A’’ was filled with 400 mL water whereas the beaker labeled ‘’B’’ was filled with 400 mL of 2M solution of NaCl. At the same temperature both the beakers were placed in closed containers of same material and same capacity as shown in the figure.

At a given temperature, which of the following statements is correct about the vapour pressure of pure water and that of NaCl solution.

1. Vapour pressure in container (A) is more than that in container (B)
2. Vapour pressure in container (A) is less than that in container (B)
3. Vapour pressure is equal in both the containers
4. Vapour pressure in container (B) is twice the vapour pressure in container (A)

Answer: (i) Vapour pressure in container (A) is more than that in container (B)

Question: 23 – If two liquids A and B form minimum boiling azeotrope at some specific composition, then _ _ _ .

1. A – B interactions are stronger than those between A – A or B - B
2. Vapour pressure of solution increases because more number of molecules of liquids A and B can escape from the solution
3. Vapour pressure of solution decreases because less number of molecules of only one of the liquids escape from the solution
4. A – B interactions are weaker than those between A – A or B – B

Answer: (iv) A – B interactions are weaker than those between A – A or B – B

Question: 24 – 4L of 0.02 M aqueous solution of NaCl was diluted by adding one litre of water. The molality of the resultant solution is _ _ _ .

1. 0.004
2. 0.008
3. 0.012
4. 0.016

Answer: (iv) 0.016

Question: 25 – On the basis of information given below mark the correct option.

Information: On adding acetone to methanol some of the hydrogen bonds between methanol molecules break.

1. At specific composition, methanol-acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult’s Law
2. At specific composition, methanol-acetone mixture forms maximum boiling azeotrope and will show positive deviation from Raoult’s Law
3. At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show negative deviation from Raoult’s Law
4. At specific composition methanol-acetone mixture will form maximum boiling azeotrope and will show negative deviation from Raoult’s Law

Answer: (i) At specific composition, methanol-acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult’s Law

Question: 26 – KH value for Ar(g), CO2(g), HCHO(g) and CH₄(g) are 40.39, 1.67, 1.83 x 10 – 5 and 0.413 respectively.

Arrange these gases in the order of the increasing solubility.

1. HCHO < CH₄ < CO₂
2. HCHO < CO₂ < CH₄ < Ar
3. Ar < CO₂ < CH₄ < HCHO
4. Ar < CH₄ < CO₂ < HCHO

Answer: (iii) Ar < CO₂ < CH₄ < HCHO

Note: In the following questions, two or more options may be correct.

Question: 27 – Which of the following factor (s) affect the solutbility of a gaseous solute in the fixed volume of liquid solvent?

1. Nature of solute
2. Temperature
3. Pressure

1. (a) and (c) at constant T
2. (a) and (b) at constant P
3. (b) and (c) only
4. (c) only

Answer: (i) (a) and (c) at constant T (ii) (a) and (b) at constant P

Question: 28 – Intermolecular forces between two benzene molecules are nearly of same strength as those between two toluene molecules. For a mixture of benzene and toluene, which of the following are not true?

(iii) This will form minimum boiling azeotrope

(iv) These will not form ideal solution

Answer: (iii) This will form minimum boiling azeotrope and (iv) These will not form ideal solution

Question: 29 – Relative lowering of vapour pressure is a colligative property because _ _ _.

1. It depends on the concentration of a non-electrolyte solute in solution and does not depend on the nature of the solute molecules.
2. It depends on number of particles of electrolyte solute in solution and does not depend on the solute particles.
3. It depends on the concentration of a non-electrolyte solute in solution as well as on the nature of the solute molecules.
4. It depends on the concentration of an electrolyte or non-electrolyte solute in solution as well as on the nature of solute molecules.

Answer: (i) It depends on the concentration of a non-electrolyte solute in solution and does not depend on the nature of the solute molecules.

(ii) It depends on number of particles of electrolyte solute in solution and does not depend on the solute particles.

Question: 30 – Van’t Hoff factor I is given by the expression_ _ _ _ _ .

Question: 31 – Isotonic solutions must have the same _ _ _ _ .

1. Solute
2. Density
3. Elevation in boiling point
4. Depression in freezing point

Answer: (iii) Elevation in boiling point

(iv) Depression in freezing point

Question: 32 – Which of the following binary mixtures will have same composition in liquid and vapour phase?

1. Benzene - Toluene
2. Water – Nitric acid
3. Water – Ethanol
4. n – Hexane – n – Heptane

Answer: (ii) Water – Nitric acid and

(iii) Water – Ethanol

Question: 33 – In isotonic solutions _ _ _ _ _ .

1. solute and solvent both are same
2. osmotic pressure is same
3. solute and solvent may or may not be same
4. solute is always same, solvent may be different

Answer: (ii) osmotic pressure is same and

(iii) solute and solvent may or may not be same

Question: 34 – For a binary ideal liquid solution, the variation in total vapour pressure verses composition of solution is given by which of the curves?

Answer: (i) and (iv)

Question: 35 – Colligative properties are observed when _ _ _ _ _.

1. A non-volatile solid is dissolved in a volatile liquid
2. A non-volatile liquid is dissolved in another volatile liquid
3. A gas is dissolved in non-volatile liquid
4. A volatile liquid is dissolved in another volatile liquid

Answer: (i) A non-volatile solid is dissolved in a volatile liquid and

(ii) A non-volatile liquid is dissolved in another volatile liquid

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