What is the vapor pressure in Pa of an aqueous solution that has a solute mole fraction of 0.250?

Data: Vapor pressure of water = 25.756 mmHg at 25°C

1.00 mmHg = 133.3 Pa

Question

What is the vapor pressure in Pa of an aqueous solution that has a solute mole fraction of 0.250?

Data: Vapor pressure of water = 25.756 mmHg at 25°C

1.00 mmHg = 133.3 Pa

| General Chemistry 2

Accepted Answer

Raoult’s Law:

P_water = x_water P⁰_water

P_water = vapor pressure of the aqueous solution

x_water = mole fraction of water in the solution

P⁰_water = vapor pressure of the pure water

x_water + x_solute = 1 ⇒ x_water = 1 - 0.250 = 0.750

P_water = 0.750 x 25.756 = 19.3 mmHg

P_water = 19.3 mmHg x $\frac{133.3 Pa}{1.00 mmHg}$ = 2.57 x 10³ Pa

Exercise 5 | Colligative Properties of Solutions