The amount of Glucose to be dissolved in 500g of water so as to produce the same lowering in vapour pressure as that of 0.2 molal aqueous urea solution

$$\begin{gathered} \mathrm{For} \mathrm{urea} \mathrm{solution}, \mathrm{m}=0.2 \\ \mathrm{RLVP}={\mathrm{X}}_{\mathrm{s}}=\frac{\mathrm{m}}{\mathrm{m}+\left({\displaystyle \frac{1000}{\mathrm{MW} \mathrm{of} \mathrm{solvent}}}\right)} \\ \mathrm{RLVP}=\frac{0.2}{0.2+\left({\displaystyle \frac{1000}{18}}\right)}=0.0036=0.36\times {10}^{-2} \\ \mathrm{For} \mathrm{glucse} \mathrm{sol}. \\ \mathrm{RLVP}=\frac{{\mathrm{n}}_{\mathrm{s}}}{{\mathrm{n}}_{\mathrm{s}}+{\mathrm{n}}_{\mathrm{o}}}=\frac{{\mathrm{n}}_{\mathrm{s}}}{{\mathrm{n}}_{\mathrm{o}}} \\ 0.36\times {10}^{-2}=\frac{{\mathrm{w}}_{\mathrm{s}}/180}{500/18} \\ {\mathrm{w}}_{\mathrm{s}}=18\mathrm{g} \end{gathered}$$