Question

Two liquids A and B are mixed in 1 : 4 mole ratio to from an ideal solution. If they exert vapour pressures of 75 mmHg and 22 mmHg respectively, the mole fraction of liquid of A in the vapour phase would be

• A. 0.46
• B. 0.66
• C. 0.56
• D. 0.76

Answer 1

The correct option is A 0.46

Explanation:

According to Raoult's law, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component multiplied by the vapor pressure of that component in the pure state.

and

where, x = mole fraction

= pressure in the pure state

According to Dalton's law, the total pressure is the sum of individual pressures.

given

The mole fraction of liquid a in vapor phase is given by:

Hence option A is correct answer