Question

The vapour pressure of two pure liquids $\left(A\right)$ and $\left(B\right)$ are $100$ and $80torr$ respectively. The total vapour pressure of solution obtained by mixing $2$ moles of $\left(A\right)$ and $3$ moles of $\left(B\right)$ would be :-

• A. $120torr$
• B. $36torr$
• C. $88torr$
• D. $180torr$

Answer 1

Answer: (C)

$88torr$

Total vapour pressure $P=P_A+P_B$

$P_A=100\times \frac{2}{2+3}=100\times \frac{2}{5}=40$ torr

$P_B=80\times \frac{3}{2+3}=80\times \frac{3}{5}=48$ torr

$P_{Total}=P_A+P_B=40+48=88$ torr.