Question

The vapor pressure of pure Freon 11 and pure Freon 12 at 25ᵒ C are 15 lb/in2 and 84 lb/in2 respectively. In the preparation of pharmaceutical aerosols, these two propellants are mixed together and the mole ratio of Freon 11 in the mixture is 0.6. Compute the partial vapor pressures of each of Freon 11 and Freon 12 and total vapor pressure of the mixture, assuming that the mixture follows Raoult’s law?

Answer 1

let mol of freon-11 = 0.6 mol

then mol of freon-12 = 1 mol so that ratio is 0.6

mole fraction of freon-11,

X(freon-11) = mol of freon-11 / total mol

= 0.6 / (1+0.6)

= 0.6/1.6 mol

p(freon-11) = po(freon-11)*X(freon-11)

= 15 lb/in^2 * (0.6/1.6)

= 5.625 lb/in^2

mole fraction of freon-12,

X(freon-11) = mol of freon-11 / total mol

= 1 / (1+0.6)

= 1/1.6 mol

p(freon-12) = po(freon-12)*X(freon-12)

= 84 lb/in^2 * (1/1.6)

= 52.5 lb/in^2

total pressure = sum of individual pressures

= 5.625 lb/in^2 + 52.5 lb/in^2

= 58.125 lb/in^2

Answer:

5.625 lb/in^2

52.5 lb/in^2

58.125 lb/in^2