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Homework Help: Calculating Freezing and Boiling Points

  1. Dec 10, 2007 #1
    1. The problem statement, all variables and given/known data
    Calculate the freezing point and boiling point of each of the following solutions using the observed van't Hoff factors in Table 11.6.

    (a) 0.070 m MgCl2
    Temp Freezing?

    Temp Boiling?

    (b) 0.020 m FeCl3
    Temp Freezing?

    Temp Boiling?

    2. Relevant equations
    Change in T= imK
    i=Van't Hoff factor
    K=freezing point depression or boiling point elevation

    3. The attempt at a solution
    I don't know what the change in temp is so I can't solve for K.
    Tf MgCl2- Change in T= (3)(.07)K Don't know K or T
  2. jcsd
  3. Dec 11, 2007 #2
    ∆Tb=New boiling point-Boiling point of pure solvent
    ∆Tf=Freezing point of pure solvent-New freezing point,
    now knowing boiling/freezing point of the pure solvent, i, m and K(which will be given) you can find the new boiling/ freezing point.
  4. Dec 11, 2007 #3


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    K is a property of the solvent. It has a specific value for every solvent, and can be looked up in your textbook, or a handbook, or on the web.

    See the tables on this page: http://dbhs.wvusd.k12.ca.us/webdocs/Solutions/BP-Elev-and-FP-Lower.html [Broken]
    Last edited by a moderator: May 3, 2017
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