Question

$6g$ of non volatile solution is dissolved in $90g$ of water, such that the lowering in vapour pressure is $2\%$. The molecular weight of the solute is

• A. $65$
• B. $92$
• C. $60$
• D. $80$

Answer 1

The correct option is C $60$

Given

$w_2=6$ g

$w_1=90$ g

$M_1=18$ g

$\Delta p_1=0.02$

Let take, $p_1^0=100$

$p_1=98$

$\frac{p_1^0-p_1}{p_1^0}=\frac{w_2\times M_1}{M_2\times w_1}$

$\frac{2}{100}=\frac{6\times 18}{M_2\times 90}$

$M_2=60$ g