[biospy]

Here is the question:

At 63.5 C, the vapor pressure of water is 175 torr and the pressure of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of water and ethanol. (a) what is the mole fraction of ethanol in the solution?

I put .28
is that correct?

b- assume ideal solution behavior, what is the vapor pressure of the solution at 63. 5 C

I put 238 torr...correct?

c- what is the mole fraction of ehtanol in the vapor above the solution?

This is what i need help with...I cant get it!

[mdlhvn]

Absolutely correct, and the answer of c) mole fraction of ethanol in the vapor is 0.53. Because you have the correct answer in a and b, so I think you know the method.

OK!

[biospy]

okay thanks

but the answer to c is actually .47.....i found the answer in the book because its (.28)(400)/238=.47

but thanks for the other checks

[mdlhvn]

Oh, sorry for this inconvinience. I have confused. It's the mole fraction of water, 0.53, then absolutely that of ethanol is 0.47

You're welcome!