Question

The vapour pressure of a dilute solution of glucose is 750 mm of Hg at 373 K. The mole fraction of solute is _____________.

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

Answer 1

Answer: (D)

$\frac{1}{76}$

Given, vapor pressure of solution = 750 mm of Hg

Vapour pressure of pure water = 760 mm of Hg

$\frac{P^0-P_S}{P^0}=\frac{n}{n+N}(P^0=760mm$ at 373 K)

$\therefore \frac{n}{n+N}=\frac{760-750}{760}=\frac{1}{76}$

Hence mole fraction of solute = $\frac{1}{76}$