31) Which of the following pair of liquids are immiscible?

a) Acetone + water.
b) Benzene + water.
c) Ethanol + water.
d) Acetic acid + water.

ANSWER : Benzene + water.

32) Osmotic pressure of a solution is:

a) Inversely proportional to its absolute temperature.
b) Inversely proportional to its centigrade temperature.
c) Directly proportional to its centigrade temperature.
d) Directly proportional to its absolute temperature.

ANSWER : Directly proportional to its absolute temperature.

33) When 100 g of sucrose ( mol.mass = 342 ) is added to 100 g of water, the vapour pressure is lowered to 0.125 mm Hg at 25°C. What is the vapour pressure of pure water at 25°C.

a) 2.38 mm Hg.
b) 1.15 mm Hg.
c) 0.11 mm Hg.
d) 23.8 mm Hg.

ANSWER : 23.8 mm Hg.

34) If the solvent boils at a temperature T₁ and the solution at a temperature T₂ , then the elevation of boiling point is given by:

a) T₁ + T₂.

b) T₁ – T₂.

c) T₂ – T₁.

d) None of the above.

ANSWER : T₂ – T₁.

35) The ratio of elevation in B.P to molality of solution is known as:

a) Molar elevation constant.
b) Mole elevation constant.
c) Normal elevation constant.
d) Molal elevation constant.

ANSWER : Molal elevation constant.

36) Arrange the following aqueous solutions in the order of their decreasing boiling points.

i) 10-4 M Nacl.
ii) 10-3 M urea.
iii) 10-3 M MgCl2.
iv) 10-2 M Nacl.

a) (ii) > (i) = (iii) < (iv).
b) (i) > (ii) > (iii) > (iv).
c) (ii) > (i) > (iii) > (iv).
d) (iv) > (iii) > (ii) > (i).

ANSWER : (iv) > (iii) > (ii) > (i).

37) Molecular weight of non-volatile and soluble solute can be determined by:

a) Elevation of boiling point.
b) Depression in freezing point.
c) Lowering of vapour pressure.
d) Osmotic pressure.

ANSWER : Elevation of boiling point.

38) The boiling point of Benzene, Ethanol, Octane and Pentane are 80°C, 78°C, 126°C and 36°C respectively. Which of the following will show highest vapour pressure at room temperature.

a) Benzene.
b) Octane.
c) Pentane.
d) Entahol.

ANSWER : Pentane.

39) When a solute is dissolved in water it shows:

a) decrease in freezing point of water.
b) decrease in boiling point of water.
c) increase in vapour pressure of water.
d) all of the above.

ANSWER : decrease in freezing point of water.

40) When sugar is added to water, what is the change observed in boiling and freezing points of water?

a) Both boiling point and freezing point decreases.
b) Both boiling point and freezing point increases.
c) Boiling point increases and freezing point decreases.
d) Boiling point decreases and freezing point increases.

ANSWER : Boiling point increases and freezing point decreases. 

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