Freezing Point of the Solvent MCQs

The normal freezing point of a pure liquid is the temperature at which the vapor pressure of the solid phase equals the vapor pressure of the liquid phase under atmospheric pressure. At this freezing point, the solid and liquid phases of the solvent are in equilibrium. When a solution freezes, it is not the solution itself that solidifies, but rather the pure solvent that separates out from the solution. Therefore, the freezing point of a solution is the temperature at which the vapor pressure of the solid solvent and the vapor pressure of the liquid solution are equal. Since the vapor pressure of a solution is lower than that of the pure liquid solvent, equilibrium can only be achieved when the vapor pressure of the solid solvent is lower.

Which one of the following gases has the lowest value of Henry’s law constant?

(a) N₂
(b) He
(c) H₂
(d) CO₂

The amount of urea to be dissolved in 500 cc of water (K = 1.86°C mol⁻¹) to produce a depression of 0.186°C in the freezing point is

(a) 9g
(b) 6g
(c) 3g
(d) 0.3g

The empirical formula of a nonelectrolyte is CH₂O. A solution containing 6g of the compound exerts the same osmotic pressure as that of a 0.05M glucose solution at the same temperature. The molecular formula of the compound is

(a) C₂H₄O₂
(b) C₃H₆O₃
(c) C₅H₁₀O₅
(d) C₄H₈O₄

A 500g toothpaste sample has 0.2g fluoride concentration. What is the concentration of F in terms of ppm level?

(a) 250
(b) 300
(c) 400
(d) 1000

Which of the following 0.10M aqueous solutions will have the lowest freezing point?

(a) Al₂(SO₄)₃
(b) C₆H₁₂O₆
(c) KCl
(d) C₁₂H₂₂O₁₁

Which statement is true for a solution of 0.020M H₂SO₃?

(a) 2 liters of the solution contain 0.020 mole of SO₄²⁻
(b) 2 liters of the solution contain 0.080 mole of H₃O⁺
(c) 1 liter of the solution contains 0.020 mole of H₃O⁺
(d) None of these

If at a certain temperature the vapor pressure of pure water is 25 mm Hg and that of a very dilute aqueous urea solution is 24.5 mm Hg, the molality of the solution is

(a) 0.02
(b) 1.2
(c) 1.11
(d) 0.08

A 0.5 molal solution of ethylene glycol in water is used as a coolant in a car. If the freezing point constant of water is 1.86°C per mole, the mixture shall freeze at

(a) 0.93°C
(b) -0.93°C
(c) 1.86°C
(d) -1.86°C

The molar mass of the solute sodium hydroxide obtained from the measurement of the osmotic pressure of its aqueous solution at 27°C is 25 g/mol. Therefore, its ionization percentage in this solution is

(a) 75
(b) 60
(c) 80
(d) 70

If 10 ml of 0.1M aqueous solution of NaCl is divided into 1000 drops of equal volume, what will be the concentration of one drop?

(a) 0.01M
(b) 0.10M
(c) 0.001M
(d) 0.0001M