The vapour pressure of pure benzene is `639.7 mm Hg` and the vapour pressure of solution of a solute in benzene at the temperature is `631.9 mm Hg`. Calculate the molality of the solution.

Answer

0.162 m

Explanation

Solute-B, Benzene-A
`"Let molality of solution=X"`
`(P^(0)-P_(solution))/(P^(0))=X_(solute)`
`(639.7-631.7)/(639.7)=X_(solute)`
`m=(X_(solute))/((1-X_(solute)))xx1000/78`
`"therefore molality of solution=0.162 m"`