Last modified: Sun 01/17/2016 03:43:42 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 some solutions. In the table below are the experimental parameters for three different substances. Open the Colligative property activity (it will open in a new window), resize the window so you can see the equipment and the table in this window and follow the instructions. On the apparatus displayed in the window, click the radio button so the switch is on Cold. That will do freezing point depressions. Select the solute and solvent by clicking on the appropriate Radio Button, and use the sliderbar to added the mass of solute and solvent. Determine the freezing point of the sucrose solutions in Exp 1 and 3 and enter the experimental freezing point in the appropriate cell. For freezing point data select the Cold Bath.

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 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 glucose.

7. Now compare the measured freezing points between sucrose and 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?