CHEM 214 General Chemistry II Lab - Experiment 004: Determination of the Molecular Weight of Isopropyl Alcohol via Freezing Point Depression

CHEM 214 General Chemistry II Lab - Experiment 004: Determination of the Molecular Weight of Isopropyl Alcohol via Freezing Point Depression References: Suzanne Slayden, 2018, Chemistry 213, 214, 272 Laboratory Experiments, 7th Edition, pages 179-185. George Mason University, Department of Chemistry and Biochemistry. Freezing Point Depression; 2020. Freezing Point Depression, Distance Learning Summer 2020, accessed via Blackboard. Purpose The purpose of the experiment is to determine the molecular weight of isopropyl alcohol. This will be done by taking a freezing point measurement of an aqueous solution of the isopropyl alcohol. The anticipated outcome is that the experimental molecular weight of isopropyl alcohol will match the theoretical molecular weight of isopropyl alcohol. Materials • 4 mL Isopropyl Alcohol • Freezing Point Apparatus o Test Tube o Rubber Stopper o Thermometer o Stirrer • Ice • Distilled Water • Rock Salt • Large Beaker • Graduated CylinderProcedure 1. Make a cold bath with equal parts ice and rock salt with a small amount of water in the large beaker. Stir. Make sure the temperature of the bath is at least 10°C or below. 2. Use distilled water to rinse the freezing point apparatus and shake out any leftover water in the test tube. Use a graduated cylinder to measure 15.0 mL of distilled water and transfer it to the test tube. Hold the thermometer and stirrer in place using the stopper and stopper the test tube. Clamp the test tube to be completely inside the cold bath. 3. Consistently move the stirrer up and down to keep the water agitated. Pause the stirrer regularly every 30 seconds to record time and temperature. Continue this process until the temperature readings are the same for five readings in a row, or until the water has become frozen enough to no longer be able to stir. Let frozen water thaw to room temperature, then repeat. 4. Measure 4 mL of isopropyl alcohol, then transfer to the freezing point apparatus. 5. Place freezing point apparatus in cold bath and repeat the agitation procedure, recording time and temperature every 30 seconds, as well as the freeze/thaw procedure in Step 3.