Liquids A and B form an ideal solution. At a given temperature $p_{A}^{0} = 400 mmHg$ and $p_{B}^{0} = 200 mmHg$ . For a liquid mixture with $x_{A} = 0.40$ , find the mole fraction of A in the vapour in equilibrium with it (two decimal places).

Numerical answer type, tolerance 0.005.

Answer: 0.57

p_{A} = 0.40 \times 400 = 160

and

p_{B} = 0.60 \times 200 = 120

mmHg, so

P = 280

mmHg.

y_{A} = p_{A} / P = 160/280 = 0.5714

, i.e.

0.57

to two decimals.