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6. Weigh and record the mass of a plastic weigh boat. 7. Tare the balance with the weigh boat on the balance. 8. Weigh approximately 5 grams of lauric acid into the weigh boat. 9. Record this mass on your data sheet. 10. Transfer the lauric acid to the test tube. Some lauric may remain in the weigh boat. 11. Reweigh the weigh boat. Record this mass on your data sheet. Use the two masses of lauric acid to find the exact mass of lauric acid added to the test tube. 12. Place the test tube with the lauric acid in the water bath. 13. Once the lauric acid begins to melt, insert the thermometer to the test tube. Gently stir the acid with the thermometer using a slight up-down motion until it is fully melted. 14. Make sure that the temperature is above 50 °C. 15. Remove the test tube from the water bath and record the temperature. This will be the temperature at time 0. 16. Record the temperature every 20 seconds for 10 minutes.
Experiment #1: Determination of Molar Mass using Freezing Point Depression 3 17. Make a record on the data table of the temperature at which the solid crystals first appear in the test tube. 18. Continuously stir the lauric acid during the cooling process by gently moving the thermometer in a slight up-down motion. If the thermometer becomes hard to move, simply stop moving the thermometer and just record the temperature. •Trying to move the thermometer in solidified lauric acid could cause the thermometer to break. Use caution when handling/moving the thermometer. 19. At this point, the data is complete for the lauric acid, set aside the test tube of lauric. Make sure you don’t remove the thermometer. 20. Take the weigh boat and wipe out any remaining lauric acid. 21. Weigh and record the weigh boat again. 22. Tare the balance and add approximately 1 gram of benzoic acid. 23. Add the benzoic acid to the test tube that contains the solid lauric acid. Use caution when added the benzoic acid since the thermometer is still in the test tube. 24. Reweigh the weigh boat and record the mass. 25. Add the test tube to the hot water bath. Don’t try to stir the contents of the test tube with the thermometer until it is almost completely melted. Stir the contents of the test tube to ensure that sample is completely mixed.