2.9 Vapour pressure of pure water at is of urea is dissolved in of water. Calculate the vapour pressure of water for this solution and its relative lowering.
Given that vapour pressure of pure water,
Moles of water :
Moles of urea :
Let the vapour pressure of water be pw.
By Raoult's law, we get :
or pw = 23.4 mm of Hg.
Relative lowering :- Hence, the vapour pressure(v.P) of water in the solution = 23.4 mm of Hg
and its relative lowering = 0.0173.