The relative lowering of vapour pressure of a solution containing 6 g of urea dissolved in 90 g of water is

Wt. of urea$={\mathrm{W}}_1=6\mathrm{g}$

GMW of urea$={\mathrm{M}}_1=60\mathrm{g}$

Wt of water$={\mathrm{W}}_2=90\mathrm{g}$

GMW of water$={\mathrm{M}}_2=18\mathrm{g}$

According to Raoult’s law.

$\mathrm{R}.\mathrm{L}.\mathrm{V}.\mathrm{P}=\frac{{\mathrm{W}}_1}{{\mathrm{M}}_1}\times \frac{{\mathrm{M}}_2}{{\mathrm{W}}_2}$

$=\frac{6}{60}\times \frac{18}{90}$

$=\frac{1}{50}$

=0.02(Near by)