[sugarhillave]

in a soultion of sodium chloride in water, the vapor pressure is 19.6 torr at 25 degrees C.

i converted the pressure to 298.15 K and the temperature to .0258 atm.

i need to find out the mole fraction of NaCl, but i dont understand how to get either grams of moles.

[savoy7]

Maybe your thinking too much about moles and mass.

Try looking at water's vapor pressure.  Since you started with C and torr, I'll stay with those units.  At 25 C, pure water has a vapor pressure of 23.8 torr.


In your problem, the salt water solution has a vapor pressure of 19.6 torr.  

Why did the vapor pressure change?  If you can answer that, you should be on your way to the correct answer.