Part A: If 0.440 mol of a nonvolatile nonelectrolyte are dissolved in 3.90 mol o
ID: 568634 • Letter: P
Question
Part A: If 0.440 mol of a nonvolatile nonelectrolyte are dissolved in 3.90 mol of water, what is the vapor pressure PH2O of the resulting solution? The vapor pressure of pure water is 23.8 torr at 25 C .
Express your answer with the appropriate units.
21.4 torr
Part B. A solution is composed of 1.90 mol cyclohexane (Pcy=97.6 torr) and 2.50 mol acetone (Pac=229.5 torr). What is the total vapor pressure Ptotal above this solution?
Express your answer with the appropriate units
Ptotal: 173 torr
Part C: As you saw in Part B, the vapor above the cyclohexane-acetone solution is composed of both cyclohexane vapor and acetone vapor. What mole fraction of the vapor above the solution, Xcy(vapor), is cyclohexane?
Express your answer numerically.
PH2O =21.4 torr
Explanation / Answer
1) torr is just the unit of pressure meaning mm Hg.
760 torr = 760 mm Hg = 1 atmosphere
The mole fraction of water in the solution is:
3.90 mol / (3.90 +0.440 mol) = 0.898
The vapor pressure of the solution, using the Raoult's Law is: P = 0.898 X 23.8
= 21.37 torr