1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Vapor Pressures of Solutions

  1. Feb 3, 2004 #1
    Here is the question:

    A solution of sodium chloride in water has a vapor pressure of 19.6 torr at 25 degrees celsius. What is the mole fraction of NaCl in this solution? The vapor pressure of pure water is 23.8 torr at 25 degrees celsius.
    Here's what I need help with:

    I am able to determine the mole fraction for H20 = .824
    because I took Psoln = XsolventP^0solvent (Raoult's Law) and then I did this

    Psoln divided by P^0solvent to get Xsolvent (kie solvent(mole fraction of solvent or H20)).

    I got .824 for the mole fraction of H20 but now I am unsure about how to find the mole fraction of the solute (NaCl).


  2. jcsd
  3. Feb 3, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper

    1 - mole fraction of water = mole fraction of solute.
    Last edited: Feb 3, 2004
  4. Feb 3, 2004 #3

    How did you formulate this, GeneralChemtutor?

    Does that mean .824 H20 solvent = .824 NaCl solute?


    If this is true . . . doesn't it need to be 2(.824)? B/c ionic solute's dissolve . . . like this -> NaCl -> 1 mol Na + 1 mol Cl ??
    Last edited: Feb 3, 2004
  5. Feb 3, 2004 #4
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Vapor Pressures of Solutions
  1. Vapor Pressure (Replies: 3)

  2. Vapor pressure (Replies: 1)

  3. Vapor pressure (Replies: 1)

  4. Vapor pressure (Replies: 6)