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°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, the vapor pressure of the solution is determined solely by the amount of water present. We can use Raoult's Law to calculate the vapor pressure of the solution:

P = X_water * P° water

where P 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 same temperature (in this case, 35°C).

First, we need to calculate the mole fraction of water in the solution:

total moles = 6.50 mol + 0.300 mol + 0.200 mol = 7.00 mol
X_water = 6.50 mol / 7.00 mol = 0.929

Next, we can substitute into Raoult's Law:

P = 0.929 * 42.2 torr = 39.2 torr

Therefore, the vapor pressure of the solution at 35°C is 39.2 torr (Choice D).

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