One litre solution X has x g of urea dissolved in it. Another one litre solution Y has xg of KCl dissolved in it. Find the ratio of lowering of vapour pressures of the solutions X and Y.

Explanation

The ratio of concentration = The ratio of number of moles
The mole ratio =`x/60:x/74.6=7.46 :6`
Urea is unionised even in dilute solutions and hence, van.t Hoff factor, i = 1. KCl is almost ionised in dilute solutions and hence, van.t Hoff factor, i 2. Hence the ratio of particles in two solutions 7.46 : 6 x 2
=7.46 : 12 =1 : 16
Since lowering of vapour pressure is a colligative property, the ratio of lowering = 1: 1.6