Question

Two liquids A and B are miscible over the whole range of composition and may be treated as ideal (obeying Raoult's Law). At 350 K the vapour pressure of pure A is 24.0 kPa and of pure B is 12.0 kPa. A mixture of 60% A and 40% B is distilled at this temperature; what is the pressure in a closed distillation apparatus from which air is excluded? in KPa

Answer 1

At the start of distillation, the pressure inside the distillation apparatus is equal to the vapour pressure of the mixture.
Here we assume the percentage of the components to be the molar percentage.
$P_{total}=P_A{X}_A+P_B{X}_B$
$P_{total}=24.0\times 0.6+12.0\times 0.4=19.2$ kPa