BCE

Last modified: Wed 12/31/1969 06:00:00 pm BCE

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Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.

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In this BCE you will collect some experimental data for the freezing point of two solutions. In the table below are the experimental parameters for two different substances. You will watch two movies to obtain the freezing point of the solution in experiment #1 and Experiment #3. A special water bath is used to cool an aqueous sucrose solution in a test tube and measure the freezing point. Determine the freezing point of the sucrose solutions in Exp 1 and 3 by watching both movies and enter the experimental freezing point in the appropriate cell in the Experimental Results table below.

Experiment #1 Movie
Experiment #3 Movie

Exp.	solute	Solvent	mass of solute (g)	mass of solvent (g)	Freezing point of solution (°C)
1	sucrose	water	1.7 g	100. g
2	sucrose	water	3.4 g	100. g	-0.18
3	sucrose	water	6.8 g	100. g
4	glucose	water	0.9 g	100. g	-0.09
5	glucose	water	1.8 g	100. g	-0.18
6	glucose	water	3.6 g	100. g	-0.36

1. Calculate the mol of sucrose, C₁₂H₂₂O₁₁ (MM = 342 g mol^-1) and the mol of glucose, C₆H₁₂O₆ (MM = 180. g mol^-1) and enter your calculated values below.

	Exp 1	Exp 2	Exp 3
mol C₁₂H₂₂O₁₁

	Exp 4	Exp 5	Exp 6
mol C₆H₁₂O₆

2. Use the mol of each solute and the mass of the solvent to calculate the molality of each of the solutions.

	Exp 1	Exp 2	Exp 3
molality C₁₂H₂₂O₁₁

	Exp 4	Exp 5	Exp 6
molality C₆H₁₂O₆

3. What pattern do you see for the mol of C₁₂H₂₂O₁₁, in Exp 1, 2 and 3. (base your response on assuming two significant figures in the number of calculated moles)?

4. What pattern do you see for the mol of C₆H₁₂O₆, in Exp 4, 5 and 6. (base your response on assuming two significant figures in the number of calculated moles)?

5. Based on the pattern of the mol of solute, and the measured freezing points in Exp 1, 2 and 3, describe the trend in freezing points of water in the three solutions containing the solute sucrose.

6. Based on the pattern of the mol of solute, and the measured freezing points in Exp 4, 5 and 6, describe the trend in freezing points of water in the three solutions containing the solute glucose.

7. Now compare the measured freezing points of water between the solutions containing sucrose and the solutions containing glucose in Exp 1 and 4, Exp 2 and 5 and Exp 3 and 6. Describe the trend do you see?

8. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

9. If there is one question you would like to have answered in lecture, what would that question be?