in ideal solution of non volatile solute B and solvent Ain 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

In first case molar ratio of solute and solvent is 2:5
So mole fraction of solvent, χA=52 + 5 = 0.71
Using Raoult's law:
p(solution) = p(pure solvent) × mole fraction of solvent
250 = p(pure solvent) × 0.71
p(pure solvent) = 352.11  mm

In second case molar ration of solute and solvent is 3:4
So mole fraction of solvent, χA=43 + 4 = 0.57
Using Raoult's law:
p(solution) = p(pure solvent) × mole fraction of solvent
p(solution) = 352.11 × 0.57 = 200.7 mm

Hence correct option is 1) 200 mm

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