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, then the weight ratio of the solvent and solute is :

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`.