Question

The vapour pressure of a dilute aqueous solution of glucose is $750\text{mm of mercury}$ at $373K$. The mole fraction of solute in the solution is:

• A. $\frac{1}{10}$
• B. $\frac{1}{76}$
• C. $\frac{1}{7.6}$
• D. $\frac{1}{35}$

Answer 1

The correct option is B $\frac{1}{76}$

For a dilute solution,
$\text{Relative lowering of vapor pressure= mole fraction of the solute}$
Given,
$\text{Pressure of the solution},P_S=750\text{mm Hg}$
$\text{Pressure of pur water},P^o=760\text{mm Hg}$

$\Rightarrow \frac{P_0-P}{P_0}=\frac{760-750}{760}=\frac{1}{76}$