The vapor pressure of pure methanol at 25 degrees Celsius is 127.2 mm Hg. If 12.20 g of potassium chloride are dissolved in 200.0 g of methanol, what is the vapor pressure of the solution?

A.123.9 mmHg
B.3.256 mmHg
C.104.3 mmHg
D142.7 mmHg

mols KCl = grams/molar mass = ?

mols methanol = grams/molar mass = ?
Xmethanol = mols methanol/total mols.
p(methanol) = i*X.methanol
i is 2 for KCl

Post your work if you get stuck.

I didn't get any of the answer choices

I got 1.95
It's .164 mol kcl
6.242 mol ch3oh
Then put the 6.242 over 6.406 and got .975
Then 2 x the .975

I gave you the wrong formula. Let me start over.

I don't get close to any of those answers.

To determine the vapor pressure of the solution, we need to make use of Raoult's law. According to Raoult's law, the vapor pressure of a solution is directly proportional to the mole fraction of the solvent in the solution.

First, let's calculate the mole fraction of methanol in the solution:

Molar mass of potassium chloride (KCl) = 74.55 g/mol
Molar mass of methanol (CH3OH) = 32.04 g/mol

We are given that 12.20 g of KCl is dissolved in 200.0 g of methanol. To calculate the mole fraction, we need to convert the masses of both substances to moles.

Number of moles of KCl = mass / molar mass = 12.20 g / 74.55 g/mol
Number of moles of CH3OH = mass / molar mass = 200.0 g / 32.04 g/mol

Now, we can calculate the mole fraction of methanol:

Mole fraction of CH3OH = number of moles of CH3OH / (number of moles of CH3OH + number of moles of KCl)

Next, we need to calculate the vapor pressure of the solution using Raoult's law:

Vapor pressure of the solution = mole fraction of CH3OH * vapor pressure of pure methanol

Using the information provided, the vapor pressure of pure methanol at 25 degrees Celsius is 127.2 mm Hg. Substitute the values into the formula to determine the vapor pressure of the solution.

Finally, compare the calculated vapor pressure of the solution to the provided answer choices. The correct answer should match the calculated vapor pressure of the solution.