Question

At $48^\circ C$ the vapour pressure of pure $CS_{2}$ is $850torr$ . A solution of $2.0 \, \, \text{g}$ of sulphur in $100g$ of $\text{C} \text{S}_{2}$ has a vapour pressure $844.9torr$ . Determine the atomicity of sulphur molecule.

• A. 1
• B. 2
• C. 4
• D. 8

Answer 1

Answer: (D)

$\Delta P=5.1torr$ ; x is atomicity of sulphur.
$\frac{\Delta P}{P_{A}^{^\circ }}=\frac{5 .1}{850}=X_{B}=\frac{\frac{2}{32 x}}{\frac{2}{32 x} + \frac{100}{76}}$
$\frac{5 .1}{850}\cong\frac{2}{32 x}\times \frac{76}{100}$
$x=\frac{2 \times 76}{32 \times 100}\times \frac{850}{5 .1}=7.92\approx8$