The vapour pressure of a solution of a non-volatile electrolyte `B` in a solvent `A` is `95%` of the vapour pressure of the solvent at the same temperature. If the molecular weight of the solvent is `0.3` times, the molecular weight of solute, the weight ratio of the solvent and solute are:

Options

A. `0.15`
B. `5.7`
C. `0.2`
D. None of these

Answer

B

Explanation

According to question `P_(s)=0.95 P_(0)`
according raoult's law `P_(s)=P_(0)X_(A)` given `M_(A)=0.3M_(B)`
`0.95_(0)=P_(0) (W_(A)/(M_(A)/(W_(A)/(M_(A))+(W_(B))/(M_(B))))) M_(A)=` molecular `wt.` of solvent
`M_(B)=` molecular `wt.` of solute
`0.95=W_(A)/((0.3M_(B))/(W_(A)/(0.3M_(B))+(W_(B))/(M_(B)))) M_(A)=` gram wt. of solvent
on solving `(W_(A))/(W_(B))=5.7`.