Colligative Properties
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Colligative Properties Lab – Freezing Point Depression & Boiling Point Elevation
Introduction
The physical properties of solutions that depend on the number of dissolved solute particles and not their
specific type are known as colligative properties. These include freezing point depression, osmotic pressure, and
boiling point elevation. In this lab, freezing point depression and boiling point elevation will be investigated.
Purpose: What is the point of completing this lab? _______________________________________________
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Materials/Apparatus: List what you see on the virtual lab bench.
Procedure:
1. Go to simulation lab below.
2. Scroll to the bottom of the page to the section Solutions – click on the Freezing-Point Depression experiment
3. Molar Mass Determination by Freezing Point Depression
Experiment #1, choose the following options: cold bath (click on the switch), and 100g of distilled H2O, click start.
Record your data in the table.
Experiment #2, choose cold water bath, 100g H2O, and 2.0g of sucrose (C12H22O11), click start. Record your data.
Experiment #3, choose cold water bath, 100 g benzene. Click start. Record your data.
Experiment #4, choose cold water bath, 100 g benzene, and 4.0g of CaCl2, click start. Record your data.
Experiment #5, choose cold water bath, add 100 g ethyl ether. Click start. Record data
Experiment #6, choose cold water bath, ,add 100 g ethyl ether and 2.0 g of NaCl. Record your data.
Experiment
1 – pure H2O
Freezing point
2- 100 gH2O & 2.0 g C12H22O11
3- 100 g benzene
4- 100 g benzene& 4.0 g CaCl2
5- 100g ethyl ether
6- 100 g ethyl ether & 2.0 g NaCl
Lab data
1. Make a data table showing the FP of the pure solvent, the FP of the solution. The Kf of each solvent and ΔT of each
solution.
2. Determine Molar Mass of the solute in each solution. Figure that out! You will need to include a data table
stating FP of pure solvent, FP of solution. Kf of each solvent. ΔT for each solution.
Colligative Properties
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Conclusion Questions
1. Why is a molality concentration scale used in the context of colligative properties and not the more common
concentration scale, molarity?
2. Assume that you have a solution of an unknown solute in cyclohexane. If the solution has a freezing point
depression of 9.50 0C, what is the molality of this solution? (The freezing point depression constant for
cyclohexane (Kf) is 20.4 0C/m).
3. Cyclohexanol, C6H11OH, is sometimes used as the solvent in molecular weight determination by freezing
point depression. If 0.253 g of benzoic acid, C6H5COOH, dissolved in 12.45 g of cyclohexanol, lowered the
freezing point of pure cyclohexanol by 6.55 0C, what is the molal freezing point constant (Kf) of this
solvent?
4. What is supercooling? How can it be minimized?
5. Distinguish between non-volatile and volatile substances. Give two examples of each.
6. Write a conclusion paragraph about how this lab re-enforces the concepts of colligative properties and any
improvements/problems with the lab.