Question

The vapour pressure of the solution containing 30 g. of non-volatile solute of molecular weight 60 in 360 gm of water approximately at ${30}^{0}c$ is: ( vapour pressure of water at ${30}^{0}c$ = 24mm of Hg )

• A. 26.8 mm
• B. 25.8 mm
• C. 23.40 mm
• D. 29.4 mm

Answer 1

The correct option is C 23.40 mm

Given

mass of solute 30g

mass of solvent 360g

the molecular mass of solute 60g

the molecular mass of solvent that is water is 18 g

The pressure of pure water is 24mmHg

Solution

$\frac{P_0-P}{P}=molesofsolute/totalno.ofmoles$

$\frac{P_0-P}{P}=\frac{\frac{30}{60}}{\frac{30}{60}+\frac{360}{180}}$

$\frac{P_0-P}{P}=1/41$

P=23.4mmHg

The correct option is C