Solution B Measured Mass of NaCl - 11.69 g Measured Volume of Water - 100.0 mL 1. Answer each question with correct significant figures and units.

Solution B

Measured Mass of NaCl - 11.69 g

Measured Volume of Water - 100.0 mL

1. Answer each question with correct significant figures and units. You must show calculations for determining each quantity. If necessary, use the molar mass of NaCl = 58.44 g/mol.

a. Determine the number of moles of NaCl in the solution. (5 points)

b. Determine the number of moles of all solutes (both cations and anions) from the number of moles of NaCl that you determined above. For this question, in addition to your calculation, explain the idea behind your calculation. (5 points)

c. Determine the mass (in kg) of solvent (assume that the density of water is 1.000 g/mL). (5 points)

d. Determine the molality (in m or mol/kg) of all solutes. (5 points)

Solution C

Measured Mass of NaCl - 5.84 g

Measured Volume of Water 100.0 mL

2. Answer each question with correct significant figures and units. You must show calculations for determining each quantity. If necessary, use the molar mass of NaCl = 58.44 g/mol.

a. Determine the number of moles of NaCl in the solution. (5 points)

b. Determine the number of moles of all solutes (both cations and anions) from the number of moles of NaCl that you determined above. For this question, in addition to your calculation, explain the idea behind your calculation. (5 points)

c. Determine the mass (in kg) of solvent (assume that the density of water is 1.000 g/mL). (5 points)

d. Determine the molality (in m or mol/kg) of all solutes. (5 points)

Solution D

Measured Mass of NaCl - 2.92 g

Measured Volume of Water - 100.0 mL

3. Answer each question with correct significant figures and units. You must show calculations for determining each quantity. If necessary, use the molar mass of NaCl = 58.44 g/mol.

a. Determine the number of moles of NaCl in the solution. (5 points)

b. Determine the number of moles of all solutes (both cations and anions) from the number of moles of NaCl that you determined above. For this question, in addition to your calculation, explain the idea behind your calculation. (5 points)

c. Determine the mass (in kg) of solvent (assume that the density of water is 1.000 g/mL). (5 points)

d. Determine the molality (in m or mol/kg) of all solutes. (5 points)

Part C: Measuring the Freezing Point of Water

Measure Freezing Point of Water

Part D: Measuring the Freezing Point of NaCl Solutions

Measured Freezing Point of Solution B - 30 degrees C

Measured Freezing Point of Solution C - 40 degrees C

Measured Freezing Point of Solution D - 50 degrees C

4. Using the measured freezing point of distilled water in Part C, calculate the freezing point depression ΔT for NaCl solutions from Part D. The freezing point depression ΔT is calculated by the following formula.

ΔT = (Measured freezing point of water in Part C) − (Measured freezing point in Part D)

a. Determine the freezing point depression ΔT for Solution B. Show your calculation. (5 points)

b. Determine the freezing point depression ΔT for Solution C. Show your calculation. (5 points)

c. Determine the freezing point depression ΔT for Solution D. Show your calculation. (5 points)

5. Determine the molal freezing point depression constant (Kf) (in °C⋅kg/mol) of water by using the data of three NaCl solutions. Use Equation 3 in the "Background and Procedure" file, the molality values of all solutes from Questions 1 - 3 and the freezing point depression (ΔT) from Question 4. In your calculation, rewrite the symbol "m" (the molality) as "mol/kg" so that the molal freezing point depression constant will have the correct unit.

Make sure to show all your work to receive credits.

a. Use the data of Solution B and determine the molal freezing point depression constant (Kf) (in °C⋅kg/mol) of water. (5 points)

b. Use the data of Solution C and determine the molal freezing point depression constant (Kf) (in °C⋅kg/mol) of water. (5 points)

c. Use the data of Solution D and determine the molal freezing point depression constant (Kf) (in °C⋅kg/mol) of water. (5 points)

6. Analysis of Results

a. Determine the average value of three molal freezing point depression constant (Kf) values of water from Question 5 (in °C⋅kg/mol). (5 points)

b. The published value for Kf of water is 1.86°C∙kg/mol (use this as the true value). Determine the % error of the average value of the molal freezing point depression constant that you found in Question 6 a. average valuetruevalue%error100%truevalue−=×

The % error is an example of the mixed operation. In order to receive the full credits, make sure to show each step of calculations. In other words, show the result of the calculation in the numerator explicitly before dividing the numbers. (5 points)