In a solution, mole fraction of solute is 0.2 , when lowering in vapour pressure is 10 mm Hg . To get…
In a solution, mole fraction of solute is 0.2 , when lowering in vapour pressure is 10 mm Hg . To get lowering of vapour pressure of 20 mm Hg , mole fraction of solute in solution is
0.2
0.4
0.6
0.8
Solution
Lowering in
vapour
pressure
$(\Delta \mathrm{P}) \propto$ mole fraction of solute $(\mathrm{x})$.
$\begin{array}{ll}
\therefore & \frac{\Delta \mathrm{P}_1}{\mathrm{x}_1}=\frac{\Delta \mathrm{P}_2}{\mathrm{x}_2} \\
\therefore & \frac{10}{0.2}=\frac{20}{\mathrm{x}_2} \\
\therefore & \mathrm{x}_2=\frac{20}{10} \times 0.2=0.4
\end{array}$
$\therefore \quad$ Mole fraction of solute will be 0.4