(a) `10 g` of a certain non-volatile solute were dissolved in `100 g` water at `20^(@) C`. The vapour pressure was lowered from `17.3555 mm` to `17.2350 mm`, calculate `m`. wt. of solute.
(b) The vapour pressure of pure water at `25^(@)C` is `23.62 mm`. What will be the vapour pressure of a solution of `1.5 g` of urea in `50 g` of water?

Explanation

(a) We know that, `(p_(0)-p)/(p)=(w_(B)xxm_(A))/(m_(B)xxw_(A))`
`(17.3555-17.2350)/(17.2350)=(10xx18)/(m_(B)xx100)`
`m_(B)=258.5`
(b) `p=p_(0)x_(A)`
`p=p_(0)x_(A)`
`p=p_(0)(n_(A))/(n_(A)+n_(B))=23.62xx((50)/(18))/((50)/(18)+(1.5)/(60))`
`p=23.41` mm Hg.