MHS AP Chemistry
Advanced Colligative Properties Lab

The purpose of this activity is to determine the phase change constant and enthalpy of phase change for a substance, and compare the experimental values with "literature" values. The inspirations for this lab were the CRC handbook tables of "Cryoscopic Constants" and "Ebullioscopic Constants." You may choose one of the following variations:

Variation 1: Freezing Point Depression

1. Determine the freezing point depression constant (kf) for a substance.
2. Use formula 1 below to find the enthalpy of fusion.
3. Look up the freezing point constant and enthalpy of fusion for your substance.
4. Calculate your percent error(s).
5. Present your data, calculations, and results in a beautiful lab report.
6. Discuss the sources of experimental error in this lab.

Variation 2: Boiling Point Elevation

1. Determine the boiling point elevation constant (kb) for a substance.
2. Use formula 2 below to find the enthalpy of vaporization.
3. Look up the freezing point constant and enthalpy of vaporization for your substance.
4. Calculate your percent error(s).
5. Present your data, calculations, and results in a beautiful lab report.
6. Discuss the sources of experimental error in this lab.

formula 1	formula 2
M is the molecular weight of the substance in question.

[MHS AP Chem page]