The vapour pressure of water at 298 K is 0.0231 bar and the vapour pressure of a solution of 108.24 g of a compound in 1000g of water at the same temperature is 0.0228 bar.Calculate the molar mass of the solute.

Answer

`150.0`

Explanation

Lowering in vapour pressure ,
` p_(A)^(@) - p_(A) = 0.0231 - 0.0228`
` = 0.0003` bar
`(p_(A)^(@) - p_(A))/(p_(A)^(@)) = (w_(B)M_(A))/(w_(A)M_(B))` (For dilute solutions).
`(0.0003)/(0.0231) = (108.24 xx 18)/(1000 xx M_(B))`
or `" " M_(B) = (108.24 xx 0.0231 xx 18)/(0.0003 xx 1000) = 150.0`