Solutions

Previous Years' CBSE Board Questions

1.2 Expressing Concentration of Solutions

Mass Percentage, Mole Fraction, Molarity, Molality

MCQ

1. Assertion (A): Molality of a solution in liquid state changes with temperature.

Reason (R): The volume of solution changes with the change in temperature.

1. Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of Assertion (A).

(d) Salt crystals in hot water (2023)

Low concentration of oxygen in the blood and tissues

of people living at high altitude is due to

(a) high atmospheric pressure

1. Both Assertion (A) and Reason (R) are correct statements, but Reason (R) is not the correct explanation of Assertion (A).
2. Assertion (A) is correct, but Reason (R) is incorrect statement.
3. Assertion (A) is incorrect, but Reason (R) is correct statement. (2020 C)

2 50 mL of an aqueous solution of glucose C₆H₁₂O₆ (Molar mass: 180 g/mol) contains 6.02 × 10²² molecules. The concentration of the solution will be

1. 0.1 M (b) 0.2 M
2. 1.0 M (d) 2.0 M

VSA (1 mark)

1. Define the following term: Molality (m) (NCERT, 1/2, Delhi 2017, 1/5 Al 2014 C) R

4 Define the following term: Molarity (M) (NCERT, 1/2, Delhi 2017, 1/5 AI 2014) R

1. Define the following term: Mole fraction (NCERT, 1/5 AI 2014 C) (R

SAI (2 marks)

ő. Calculate the molarity of 9.8% (w/W) solution of H₂SO₄ if the density of the solution is 1.02 g mL^-1. (Molar mass of <math>H_2SO_4 = 98 \text{ g mol}^{-1}</math>)

(2/5, Foreign 2014) [EV

1. Differentiate between molarity and molality of a solution. How can we change molality value of a solution into molarity value? (Delhi 2014 C) (An)

SAII (3 marks)

1. A solution of glucose (molar mass = 180 g mol^-1) in water is labelled as 10% (by mass). What would be the molality and molarity of the solution? (Density of solution = 1.2 g mL^-1)

(NCERT, 3/5, AI 2014)

1.3 Solubility

Solubility of Gas in a Liquid (Henry's Law)

MCQ

1. On dissolving ammonium chloride in water at room temperature, the solution feels cool to touch. Under which of the following conditions does salt dissolve faster?
2. Powdered salt in cold water
3. Powdered salt in hot water
4. Salt crystals in cold water
5. low temperature
6. low atmospheric pressure
7. both low temperature and high atmospheric pressure. (2023)

An unknown gas 'X' is dissolved in water at 2.5 bar

pressure and has mole fraction 0.04 in solution. The

mole fraction of 'X' gas when the pressure of gas is

doubled at the same temperature is

1. 0.08 (b) 0.04 (c) 0.02 (d) 0.92

(Term I, 2021-22) (An

VSA (1 mark)

Why aquatic animals are more comfortable in cold

water than in warm water? (1/3, 2018) Ap

Gas (A) is more soluble in water than gas (B) at the

same temperature. Which one of the two gases will

have the higher value of K_H (Henry's constant) and

why?

(1/2, Al 2016)

SAI (2 marks)

14. What is Henry's law? Give one application of it.

(2023)

State Henry's law. Why is air diluted with helium in

the tanks used by scuba divers? (2/5, 2020) An

1. State Henry's law. Calculate the solubility of CO2 in water at 298 K under 760 mm Hg. <math>(K_H \text{ for CO}_2 \text{ in water at 298 K is } 1.25 \times 10^6 \text{ mm Hg})</math> (2020)
2. State Henry's law and mention two of its important applications. (2020 C) U
3. Give reasons for the following.
4. Aquatic species are more comfortable in cold water than in warm water.
5. At higher altitudes people suffer from anoxia resulting in inability to think. (Al 2019) (Ap

1.4 Vapour Pressure of Liquid Solutions

Raoult's Law

On mixing 20 mL of acetone with 30 mL of chloroform,

the total volume of the solution is

1. < 50 mL
2. > 50 mL

MCQ

Which of the following formula represents Raoult's law for a solution containing non-volatile solute?

1. p_solute = p^o_solute · x_solute
2. <math>p = K_H \cdot x</math>
3. P_total = p_solvent
4. p_solute = p^o_solvent · X_solvent

(Term I, 2021-22) [II]

VSA (1 mark)

1. Identify which liquid will have a higher vapour pressure at 90°C if the boiling points of two liquids A and B are 140°C and 180°C, respectively.

(One word, 2020) [II]

1. Define Raoult's law.

(1/5 AI 2014C)

SAI (2 marks)

1. State Raoult's law for a solution containing volatile components. What is the similarity between Raoult's law and Henry's law? (2020, Delhi 2014) R
2. State Raoult's law for a solution containing volatile components. Name the solution which follows Raoult's law at all concentrations and temperatures.

(2/5, Foreign 2014) R

1.5 Ideal and Non-ideal Solutions

Ideal Solutions

MCQ

1. Which one of the following pairs will form an ideal solution?
2. Chloroform and acetone
3. is saturated. (Term I, 2021-22) VSA (1 mark)
4. Ethanol and acetone
5. n-Hexane and n-heptane
6. Phenol and aniline (Term I, 2021-22) (Ap)

VSA. (1 mark)

Define the following term: Ideal solution (1/2, Delhi 2017, 1/5, Al 2017 C)

Non-ideal Solutions

OR Define the following term:

Azeotrope (1/5, Foreign 2014)

SA II (3 marks)

1. (a) Differentiate between Ideal solution and Non- ideal solution.
2. 30 g of urea is dissolved in 846 g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg. (2023)

MCQ

1. <math>= 50 \, \text{mL}</math>
2. = <math>10 \, \text{mL}</math>

(Term I, 2021-22) (Ev)

VSA (1 mark)

What happens when acetone is added to pure

ethanol? (1/2, 2020) Ev

SAI (2 marks)

What type of deviation from Raoult's law is observed

by mixing chloroform and acetone?

Why is a decrease in a vapour pressure observed in

mixing chloroform and acetone? (2021C) Ap

Write two differences between ideal solutions and

non-ideal solutions.

(2/3, 2020 C, Delhi 2019, 2/5, Al 2017)

What is meant by positive deviations from Raoult's

law? Give an example. What is the sign of <math>\Delta_{mix}H</math> for

positive deviation? (Delhi 2015) OR What is meant by negative deviation from Raoult's

law? Give an example. What is the sign of <math>\Delta_{mix}H</math> for

negative deviation? (Foreign 2015)

32. What type of deviation is shown by a mixture of

ethanol and acetone? Give reason. (2/5, Al 2014)

Azeotropes

MCQ

1. An azeotropic solution of two liquids has a boiling point lower than either of the two when it
2. shows a positive deviation from Raoult's law
3. shows a negative deviation from Raoult's law
4. shows no deviation from Raoult's law

In non-ideal solution, what type of deviation shows

the formation of maximum boiling azeotropes?

(1/2, Al 2016)

Some liquids on mixing form 'azeotropes'. What are

'azeotropes'? (Delhi 2014)

SAI (2 marks)

What type of azeotropic mixture will be formed by

a solution of acetone and chloroform? Justify on the

basis of strength of intermolecular interactions that

develop in the solution. (Al 2019) U