The vapour pressure of pure water at 25^oC is 30 mm. The vapour pressure of 10% (W/W) glucose solution at 25°C is

Given, 10% (W/W) glucose solution, i.e. W_s=10g and W_o=100-10=90g

where, s=solute , o=solvent , W=weight.

p^o=30mm , P=?

$$\begin{gathered} {\mathrm{n}}_{\mathrm{s}}=\frac{10}{180}=\frac{1}{18}=0.056 ; {\mathrm{n}}_{\mathrm{o}}=\frac{90}{18}=5 \\ \frac{{\mathrm{P}}^{\mathrm{o}}-\mathrm{P}}{{\mathrm{P}}^{\mathrm{o}}}=\frac{{\mathrm{n}}_{\mathrm{s}}}{{\mathrm{n}}_{\mathrm{s}}+{\mathrm{n}}_{\mathrm{o}}} \\ \frac{30-\mathrm{P}}{30}=\frac{0.056}{0.056+5}=0.011 \\ \mathrm{P}=29.67 \end{gathered}$$