Colligative Properties Exercise

This problem set was developed by S.E. Van Bramer for Chemistry 146 at Widener University.

A series of solutions are prepared by weighing out the solute and mixing it with 100.0 mL of water. The freezing point of these solutions is determined. The results are summarized in the table below

Mass (g) NaCl TF (oC) LiF TF (oC) HCl TF (oC)
0.1000 -0.06 -0.15 -0.10
1.0000 -0.64 -1.46 -1.02
2.0000 -1.27 -2.92 -2.04
3.0000 -1.91 -4.38 -3.06
4.0000 -2.55 -5.84 -4.08
5.0000 -3.18 -7.30 -5.10

  1. Graph the data and determine the relationship between molality and freezing point for each compound: NaCl, LiF, HCl.

  2. Based upon this information, identify the general relationship between freezing point and concentration for an aqueous solution.

  3. Based upon the behavior for the freezing point of water, what do you expect will happen to the boiling points for these solutions.

  4. Next the boiling points for these solutions are obtained. Compare these results with your expected results and use this information to identify the general relationship between boiling point and concentration for an aqueous solution.

    Mass (g)NaCl TB (oC) LiF TB (oC)HCl TB (oC)
    0.1000 100.02 100.04 100.03
    1.0000 100.18 100.40 100.28
    2.0000 100.35 100.80 100.56
    3.0000 100.53 101.21 100.84
    4.0000 100.70 101.61 101.12
    5.0000 100.88 102.01 101.40

  5. Based upon the above results, predict the freezing and boiling points for a solution prepared by combining 2.5 grams of MgCl2 with 100.0 mL of water.

  6. Based upon the above results, predict the freezing and boiling points for a solution prepared by combining 2.5 grams of sucrose - C12H22O11 with 100.0 mL of water.

  7. Data for magnesium chloride and sucrose is given in the table below. Graph the data and determine the relationship between molality and freezing point and boiling point for each compound:

    Mass (g) MgCl2 TF (oC) C12H22O11 TF (oC)
    0.1000 -0.06 -0.01
    1.0000 -0.59 -0.05
    2.0000 -1.17 -0.11
    3.0000 -1.76 -0.16
    4.0000 -2.34 -0.22
    5.0000 -2.93 -0.27

    Mass (g)MgCl2 TB (oC) C12H22O11 TB (oC)
    0.1000 100.02 100.00
    1.0000 100.16 100.01
    2.0000 100.32 100.03
    3.0000 100.48 100.04
    4.0000 100.65 100.06
    5.0000 100.81 100.07

  8. Based upon this information, identify the general relationship between freezing point and concentration for an aqueous solution.

  9. Based upon the behavior for the freezing point of water, what do you expect will happen to the boiling points for these solutions.

Graphs and figures to accompany exercise discussion
This page is maintained by
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

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Last Updated 1/16/2008