Abnormal molar mass and the van't Hoff factor — practice questions

Question 1 · difficulty L2 · understanding

Match List I with List II List I List II A. van't Hoff factor, i I. Cryoscopic constant B. $$\mathrm{k_f}$$ II. Isotonic solutions C. Solutions with same osmotic pressure III. $$\mathrm{\frac{Normal\,molar\,mass}{Abnormal\,molar\,mass}}$$ D. Azeotropes IV. Solutions with same composition of vapour above it Choose the correct answer from the options given below :

• A. A-III, B-I, C-IV, D-II
• B. A-III, B-I, C-II, D-IV
• C. A-III, B-II, C-I, D-IV
• D. A-I, B-III, C-II, D-IV

Question 2 · difficulty L2 · understanding

Two solutions A and B are prepared by dissolving 1 g of non-volatile solutes X and Y, respectively in 1 kg of water. The ratio of depression in freezing points for A and B is found to be 1 : 4. The ratio of molar masses of X and Y is

• A. 1 : 4
• B. 1 : 0.25
• C. 1 : 0.20
• D. 1 : 5

Question 3 · difficulty L2 · understanding

Which one of the following 0.06 M aqueous solutions has lowest freezing point?

• A. Al 2 (SO 4 ) 3
• B. C 6 H 12 O 6
• C. KI
• D. K 2 SO 4

Question 4 · difficulty L2 · understanding

If A 2 B is 30% ionised in an aqueous solution, then the value of van't Hoff factor (i) is _______ × 10 −1 .

Question 5 · difficulty L2 · understanding

25 mL of an aqueous solution of KCl was found to require 20 mL of 1 M $$\mathrm{AgNO_3}$$ solution when titrated using $$\mathrm{K_2CrO_4}$$ as an indicator. What is the depression in freezing point of KCl solution of the given concentration? _________ (Nearest integer). (Given : $$\mathrm{K_f=2.0~K~kg~mol^{-1}}$$) Assume 1) 100% ionization and 2) density of the aqueous solution as 1 g mL$$^{-1}$$

Question 6 · difficulty L2 · understanding

Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4 K. The ratio of molal elevation constant to molal depression constant (K b /K f ) is _________.

Question 7 · difficulty L2 · understanding

2 g of a non-volatile non-electrolyte solute is dissolved in 200 g of two different solvents A and B whose ebullioscopic constants are in the ratio of 1 : 8. The elevation in boiling points of A and B are in the ratio $${x \over y}$$ (x : y). The value of y is ______________. (Nearest integer)

Question 8 · difficulty L2 · understanding

The osmotic pressure exerted by a solution prepared by dissolving 2.0 g of protein of molar mass 60 kg mol $$-$$1 in 200 mL of water at 27$$^\circ$$C is ______________ Pa. [integer value] (use R = 0.083 L bar mol $$-$$1 K $$-$$1 )

Question 9 · difficulty L2 · understanding

Of the following four aqueous solutions, total number of those solutions whose freezing point is lower than that of 0.10 M C 2 H 5 OH is __________ (Integer answer) (i) 0.10 M Ba 3 (PO 4 ) 2 (ii) 0.10 M Na 2 SO 4 (iii) 0.10 M KCl (iv) 0.10 M Li 3 PO 4

Question 10 · difficulty L2 · understanding

2 molal solution of a weak acid HA has a freezing point of 3.885$$^\circ$$C. The degree of dissociation of this acid is ___________ $$\times$$ 10 $$-$$3 . (Round off to the Nearest Integer). [Given : Molal depression constant of water = 1.85 K kg mol $$-$$1 Freezing point of pure water = 0$$^\circ$$ C]