Question

21. In ideal solution of non volatile solute B in solvent A
in 2 : 5 molar ratio has vapour pressure 250 mm.
If a another solution in ratio 3 : 4 prepared then
vapour pressure above this solution
(1) 200 mm
(2) 250 mm
(3) 350 mm
(4) 400 mm
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Answer 1

Answer:

Explanation:

molar ratio of solute and solvent is 2:5

so mole fraction of solvent,×∧=5/2+5=0.71

using Raoult's law:

p(solution)×mole fraction of solvent

250=p(pure solvent)×0.71

p(pure solvent)=352.11mm

molar ration of solute and solvent is 3:4

so mole fraction of solvent,×∧=4/3+4=0.57

p(solution)=352.11×0.57=200.7mm

therefore, the correct option is 1)200mm