Test: Vapour Pressure of Liquid Solutions (NCERT) - NEET MCQ

P_total = p_P + p_Q = p^∘_Px_P + p^∘_Qx_Q
= 80 x 0.6 + 60 x 0.4 = 72 torr.

Here, X = P_T ​= p₁ ​+ p₂ ​= Total pressure of the solution.
p₁ and p₂ ​is the partial pressure of component 1 and 2 respectively.
Y = x₂ ​= mole fraction of component 2 in the liquid phase.
Z = y₂ ​= mole fraction of component 2 in the vapour phase.
When mole fraction of component 2 in the liquid phase is 0 then mole fraction of component 2 in the vapour phase is also 0 which means the liquid is pure of component 1 only.

Mercury is non-volatile.

Vapour pressure of a solution containing non-volatile solute is less than that of the pure solvent. The decrease in vapour pressure depends upon the quantity of non-volatile solute present in it. Hence, vapour pressure of A > C > B.

The vapour pressure increases with decrease in intermolecular forces. When the forces are weak, the liquid has high volatility and maximum vapour pressure. Diethyl ether has highest vapour pressure while water has lowest vapour pressure.