At 85°c, the vapor pressure of a is 566 torr and that of b is 250 torr. calculate the composition of a mixture of a and b that boils at 85°c when the pressure is 0.60 atm. also, calculate the composition of the vapor mixture. assume ideal behavior.

Composition of the mixture:

%

%

Composition of the vapor mixture:

%

%

Explanation:

If the ideal solution model is assumed, and the vapor phase is modeled as an ideal gas, the vapor pressure of a binary mixture with and molar fractions can be calculated as:

Where and are the vapor pressures of the pure compounds. A substance boils when its vapor pressure is equal to the pressure under it is; so it boils when . When the pressure is 0.60 atm, the vapor pressure has to be the same if the mixture is boiling, so:

With the same assumptions, the vapor mixture may obey to the equation:

, where P is the total pressure and y is the fraction in the vapor phase, so:

%

The fractions of B can be calculated according to the fact that the sum of the molar fractions is equal to 1.

b. th3 n4zc4 pl4t3 15 c0nv3rg1ng w1th the s0uth 4m3ric4n pl4t3.