A solution contains 6.50 mol water, 0.300 mol sucrose, and 0.200 mol glucose. The solutes are nonvolatile. What is the vapor pressure of the solution at 35 $\circ$ C given that the vapor pressure of water is 42.2 torr?
A)35.0 torr
B)36.0 torr
C)37.0 torr
D)39.2 torr
E)39.0 torr

Question

Quizplus · Accepted Answer

Since the solutes are nonvolatile, we can assume that the vapor pressure of the solution is only due to the water component. We can use Raoult's Law to calculate the vapor pressure of the solution: 
P_soln = X_water * P_water 
where P_soln is the vapor pressure of the solution, X_water is the mole fraction of water, and P_water is the vapor pressure of pure water at the given temperature.

First, we need to calculate the mole fraction of water: 
X_water = n_water / n_total 
n_total = n_water + n_sucrose + n_glucose = 6.50 + 0.300 + 0.200 = 7.00 mol 
X_water = 6.50 / 7.00 = 0.929

Next, we can plug in the values and solve for P_soln: 
P_soln = 0.929 * 42.2 torr = 39.2 torr

Therefore, the answer is D.

A Solution Contains 6 ∘\circ∘ C Given That the Vapor Pressure of Water Is 42

A Solution Contains 6 $\circ$ C Given That the Vapor Pressure of Water Is 42