Question

The vapour pressure of two pure liquids A and B, that form an ideal solution are $100$ and $900$ torr respectively at temperature T. This liquid solution of A and B is composed of $1$ mole of A and $1$ mole of B. What will be the pressure, when $1$ mole of mixture has been vapourized?

• A. $800$torr
• B. $500$torr
• C. $300$torr
• D. None of these

Answer 1

The correct option is B $500$torr

Vapour pressure of pure A $P_A^{\circ }=100torr$

Vapour presuure of pure B $P_B=900torr$

$n_A=1mole$

$n_B=1mole$

$x_A=\frac{1}{1+1}=0.5$

$x_B=\frac{1}{1+1}=0.5$

$P=P_A^{\circ }{x}_A+P_B^{\circ }{x}_B$

$=100\times 0.5+900\times 0.5=500torr$