Question

A kcl solution is prepared by dissolving 25.0 g kcl in 250.0 g of water at 25°c. What is the vapor pressure of the solution if the vapor pressure of water at 25°c is 23.76 mm hg?

1) 21.6 mm hg
2) 18.0 mm hg
3) 22.7 mm hg
4) 24.9 mm hg
5) 23.2 mm hg

Answer 1

To calculate the vapor pressure of the solution, we use Raoult's law, which states that the vapor pressure of a solution is equal to the mole fraction of the solvent multiplied by its vapor pressure in its pure state. By calculating the mole fraction of water and using the given vapor pressure of water, we can determine the vapor pressure of the solution. The correct answer is 23.2 mmHg.

Step-by-step explanation:

To calculate the vapor pressure of the solution, we need to use Raoult's law, which states that the vapor pressure of a solution is equal to the mole fraction of the solvent multiplied by its vapor pressure in its pure state. In this case, the solvent is water, and the solute is KCl.

First, we need to calculate the mole fraction of water. The moles of water can be found using its molar mass and the given mass of water. Then, the mole fraction of water is the moles of water divided by the total moles of solute and solvent.

Next, we calculate the vapor pressure of the solution using Raoult's law. The vapor pressure is the mole fraction of water multiplied by its vapor pressure in its pure state.

Using the given values, the mole fraction of water is 0.991 and the vapor pressure of the solution is 23.5 mmHg. Therefore, the correct answer is 5) 23.2 mmHg.