CHEM 1412 Molar Mass Determination

Online CHEM 1412 Molar Mass Determination

Dallas College

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● Add tap water until 2/3 of the ice is covered.

● Stir vigorously with your stirring rod.

2. Measure 20.0 mL distilled water into a large test tube.

3. Insert a thermometer into the liquid in the large test tube.

4. Insert the test tube into the ice water bath. Make sure the ice bath water

level is above the level of the liquid inside the test tube. If it is not, add

more ice, salt and water.

5. Record the temperature of the liquid inside the test tube every 30

seconds.

6. Continue to stir until the liquid inside the test tube starts to freeze. When

the liquid starts to freeze, do not stir anymore. Be careful not to break the

thermometer by stirring it in ice! Mark the temperatures where the liquid

starts to freeze. (by an asterisk or highlight or something.)

7. Continue to monitor until the temperature is fairly constant.

8. Record the data on your Report Sheet.

9. When done, remove the large test tube from the ice bath and melt the ice

inside with the warmth of your hands or under running water.

Lab Technique Tip: Do not remove the thermometer until the liquid inside is

melted or your thermometer may break.

PART II: Freezing Point of the Solution

1. Weigh 2.0 g of unknown F (a nonelectrolyte.)

2. Record exact weight to 0.01g on your report sheet.

3. Dissolve it in the same 20.0 mL of water inside the large test tube from

Part I.

4. Mix well until dissolved.

5. Refresh the ice bath with additional ice or salt.

6. Repeat Part I, steps 3-9.