A solution is prepared by mixing 3.44 mol of acetone with 1.45 mol of cyclohexane at 30°c. calculate the χacetone and χcyclohexane in the vapor above the solution. p°acetone = 229.5 torr and p°cyclohexane = 97.6 torr.

First calculate the mole fraction of each substance:

acetone: 3.44 mol : (3.44 mol + 1.45 mol) = 0.703

cyclohexane: 1.45 : (3.44 mol + 1.45 mol) = 0.297

Raoult's Law: P (total) = P (acetone) · χ (acetone) + P (cyclohexane) · χ (cyclohexane)

P (total) = 229.5 torr · 0.703 + 97.6 torr · 0.297

P (total) = 190.3 torr

χ for acetone: 229.5 torr · 0.703 : 190.3 torr =.848

χ for cyclohexane: 97.6 torr · 0.297 : 190.3 torr =.152