Question

The vapour pressure of two liquids P and Q are 80 and 60 torr respectively. The total vapour pressure of solution obtained by mixing 3 mole of P and 2 mol of Q would be

• A. 72 torr
• B. 140 torr
• C. 68 torr
• D. 20 torr

Answer 1

The correct option is A 72 torr

Explanation :
Let X and Y be the mole fractions of P and Q respectively,

Psoln=PP° . X + PQ °. Y
$=80\times \frac{3}{5}+60\times \frac{2}{5}$

$=48+24=72$ torr