Previous Year Questions (2014-19) - Solutions Notes | EduRev

Q.1. For an ideal solution, the correct option is :    (2019)
A: Δ_mix S = 0 at constant T and P
B: Δ_mix V ≠ 0 at constant T and P
C: Δ_mix H = 0 at constant T and P
D: Δ_mix G = 0 at constant T and P
Ans: C
For ideal solution,
Δ_mix H = 0
Δ_mix S > 0
Δ_mix G < 0
Δ_mix V = 0

Q.2. The mixture that forms maximum boiling azeotrope is:    (2019)
A: Water + Nitric acid
B: Ethanol + Water
C: Acetone + Carbon disulphide
D: Heptane + Octane
Ans: A
Solutions showing negative deviation from Raoult's law form maximum boiling azeotrope. Water and Nitric acid → forms maximum boiling azeotrope.

Q.3. If molality of the dilute solutions is doubled, the value of molal depression constant (K_f) will be :-    (2017)
A: halved
B: tripled
C: unchanged
D: doubled
Ans: C
K_f does not depend on concentration of solution. It only depends on nature of solvent so it will be unchanged.

Q.4. Which of the following is dependent on temperature?    (2017)
A: Molarity
B: Mole fraction
C: Weight percentage
D: Molality
Ans: A
Temperature dependent unit is molarity.

Q.5. At 100°C the vapour pressure of a solution of 6.5 g of a solute in 100 g water is 732 mm. If K_b = 0.52, the boiling point of this solution will be :    (2016)
A: 103°C
B: 101°C
C: 100°C
D: 102°C
Ans: B


Q.6. Which of the following statements about the composition of the vapour over an ideal 1 : 1 molar mixture of benzene and toluene is correct ?
Assume that the temperature is constant at 25°C. (Given Vapour Pressure Data at 25ºC, Benzene = 12.8kPa, toluene = 3.85kPa)    (2016)
A: Not enough information is given to make a prediction.
B: The vapour will contain a higher percentage of benzene.
C: The vapour will contain a higher percentage of toluene.The vapour will contain a higher percentage of toluene.
D: The vapour will contain equal amounts of benzene and toluene.
Ans: B
Due to high partial vapour pressure of Benzene as compare to that of toluene so the mole fraction of Benzene will be higher than that of toluene. As a result the vapour will contain a higher percentage of Benzene.

Q.7. Which one is not equal to zero for an ideal solution ?    (2015)
A: ΔP = P_observed - P_Raoult
B: Δ H_mix
C: ΔS_mix
D: Δ V_mix
Ans: C
For ideal solution, ΔS_mix = 0.

Q.8. The boiling point of 0.2 mol kg^-1 solution of X in water is greater than equimolal solution of Y in water. Which one of the following statements is true in this case ?    (2015)
A: Y is undergoing dissociation in water while X under goes no change
B: X is undergoing dissociation in water
C: Molecular mass of X is greater than the molecular mass of Y.
D: Molecular mass of X is less than the molecular mass of Y.
Ans: B
Molality of solution of x = molality of solution of y = 0.2 mol/kg
By elevation in boiling point relation


Q.9. Which one of the following electrolytes has the same value of van‘t Hoff‘s factor (i) as that of Al₂(SO₄)₃ (if all are 100% ionised)    (2015)
A: K₄[Fe(CN)₆]
B: K₂SO₄
C: K₃[Fe(CN)₆]
D: Al(NO₃)₃
Ans: A


Q.10. Of the following 0.10 m aqueous solutions, which one will exhibit the largest freezing point depression?    (2014)
A: Al₂ (SO₄ )₃
B: K₂SO₄
C: KCl
D: C₆H₁₂O₆
Ans: A