Question

The vapour pressure of an aqueous solution of glucose at 100 is 710 mmHg. Hence the molality of the solution is:

• A. 2.83 m
• B. 3.675 m
• C. 16.47 m
• D. 12.5 m

Answer 1

The correct option is B 3.675 m

$\frac{P^o-P}{P^o}=x_2=\frac{n_2}{n_1}$

$\Rightarrow \frac{n_2}{n_1}=\frac{W_2/M_2}{W_1/M_1}$

As per question,

$\Rightarrow \frac{760-710}{760}=\frac{5}{76}=x_2=\frac{n_2}{n_1}$

$\Rightarrow \frac{5}{76}\times n_1=n_2$

$\Rightarrow 0.065\times \frac{1000}{18}=n_2$

$\Rightarrow 3.675=n_2$

Molality= $3.6m$