Calculate the vapour pressure at 295K of a 0.1 M solution of urea (`NH_(2)CONH_(2)`, molar mass = 60). The density of solution may be taken as 1g `cm^(-3)`. The vapour pressure of pure water at 295K is 20 mm.

Answer

1996 mm

Explanation

Weight of solute (Urea) `=0.1 xx 60 = 6g L^(-1)`
Weight of 1L solution = 1000 g
Weight of solvent `= 1000 - 6=994 g`
No. of moles of solute = 0.1
No. of moles of solvent `=(994)/(18)=55.2`
Mole fraction of solute `=(0.1)/(55.3)=1//553`
Now `(p^(0)-p)/(p^(0))=` Mole fraction of solute `=(1)/(553)`
or `(20-p)/(20)=(1)/(553) or 20-p=(20)/(553)=0.036 or p=20-0.036`
`=19.96` mm