Determination of Molar Mass by Freezing Point Depression

Authors Avatar

Determination of Molar Mass by Freezing Point Depression

Investigators:                        September 1, 2009

1. Objective:

  • To determine the molar mass of an unknown mixture by measuring the freezing point.
  • To depress the freezing point of H2O by adding Ethanol.

2. Experimental Methods:

2.1. General Procedure: The procedure was followed from the lab manual, Principles of Chemistry, CHEM 1211L & CHEM 1212L Laboratory Experiments, A Project Oriented Approach, 4th Edition, 2009-Fall, p. 105-114.

2.2. Modifications:

  • A glass beaker was used instead of a Styrofoam cup for solution run #1 & #2.
  • Data was recorded for temperature below -10°C for the solution.
Join now!

3. Experimental Results:

3.1.  Determination of a Molar Mass by Measurements of Freezing Point     Depression.

3.2. Graphs  

        3.3 Calculations

1.        Average Freezing point (pure H2O):        0.0 degrees Celsius

2.        Average Freezing point (solution):        -4.75 degrees Celsius

3.        Freezing point depression:        -4.75 degrees Celsius

4.        Molal concentration of the solution:        2.554 m

5.        Mass of the unknown. (Þ=0.785 g/mL):                5.495 g

6.        Moles of unknown:        .0638 moles

7.        Molar mass of the unknown:        86.128 g/mol

4. Discussion:

4.1. Error Analysis

  • Contaminants: It is easy ...

This is a preview of the whole essay