'W' g of a non-volatile electrolyte solid solute of molar mass 'M' g mol –1 when dissolved in 100 mL water, decreases vapour pressure of water from 640 mm Hg to 600 mm Hg. If aqueous solution of the e

Question

'W' g of a non-volatile electrolyte solid solute of molar mass 'M' g mol –1 when dissolved in 100 mL water, decreases vapour pressure of water from 640 mm Hg to 600 mm Hg. If aqueous solution of the electrolyte boils at 375 K and Kb for water is 0.52 K kg mol –1, then the mole fraction of the electrolyte solute (x2) in the solution can be expressed as (Given : density of water = 1 g/mL and boiling point of water = 373 K)

(A) .3 W M
(B) 6 W 2.6 M
(C) .6 M W
(D) .3 W

Prashant Kotian · Accepted Answer

Correct answer: A. P° = 640 mm Hg PS = 600 mm Hg P = 40 mm Hg ALLEN  moles of solute = W M solute o P i.X P   Again : Tb = i × kb × m 2 = i × 0.52 × W / M 100  M i 5.2 W   solute 1 5.2 W X i 2 M      solute 1.3 W X M  

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