A solution of LiCl in a mixture of water and methanol (CH3OH) has a vapor pressure of 39.4 mmHg at 17C and 68.2 mmHg at 27C. The vapor pressure of pure water is 14.5 mmHg at 17C and 26.8 mmHg at 27C, and the vapor pressure of pure methanol is 82.5 mmHg at 17C and 140.3 mmHg at 27C. What is the composition of the solution (in mass percent)?
I have attempted at solving this problem but my solution and answers were different from the textbook's answer.
Here is the answer from the textbook (Rightclick and click on view image to see the image better) Also, the symbol "_" is a minus sign.
But I have a problem with the textbook solution. It does not consider Raoult's Law, which says that the solution's vapor pressure will be less because of the dissolved LiCl.
Here's my solution
I don't know why the answers and solutions are different. Can anyone help me? Thanks a lot.