At `25^(@)`C , the saturated vapour pressure of water is 3.165 k Pa (23.75 mm Hg). Find the saturated vapour pressure of a 5% aqueous solution of urea (carbamide) at the same temperature.
(Molar mass of urea = 60.05 g `mol^(-1)` )

Explanation

`(P^(0)- P_(S))/(P^(0)) = n_(2) = (n_(2))/(n)`
(for dilute solution `n_(2) lt lt n_(1)`)
`(P^(0) - P_(S))/(P^(0)) = (W_(2) xx M_(1))/(W_(1) xx M_(2))`
Given `P^(0)` = 3.165 kPa, `W_(2) = 5 g, W_(1) = 95 ` g
`M_(2) = 60.05 g "mol"^(-1), M_(1) = 18 g mol^(-1)`
`(3.165 - P_(s))/(3.165) = (5 xx 18)/(60.05 xx 95) = 0.0158`
3.165` - P_(s) ` = 0.049
`P_(s) = ` 3.116 kPa