Question

At ${100}^{\circ }C$, benzene & toluene have vapour pressure of $1375$ & $558torr$ respectively. Assuming these two form an ideal binary solution that boils at $1atm$ & ${100}^{\circ }C$. What is the composition of vapour issuing at these conditions?

• A. $x_b=0.2472,y_b=0.4473$
• B. $x_b=0.4473,y_b=0.2472$
• C. $x_b=0.584,y_b=0.104$
• D. $x_b=0.104,y_b=0.584$

Answer 1

The correct option is A $x_b=0.2472,y_b=0.4473$

We know, $P_T=P_A^{\circ }{X}_a+P_B^{\circ }{X}_b$

1 atm pressure = 760 torr

$760=1375X_a+558(1-X_a)$

$760=817X_a+558$

$202=817X_a$

Therefore, $X_a=0.247$ and $Y_b=0.4473$