Question

I am doing a latenitelab on Molecular Mass by Freezing Poing Depression. I am stuck on three questions.

1.Suppose you added 4.000 g of FP sample #1 instead of 2.000 g, what would happen to the freezing point temperature of the water?

2. Suppose you dissolve 154.286 g of sodium chloride in 2.00 L of water. What is the molality of the solution given that the molar mass of sodium chloride is 58.44 g/mol and the density of water is 1.000 g/mL?

3. Calculate the molar mass of FP sample 2.

Lab Notes:

1. I took an empty test tube and placed it on the balance. I zeroed the balance.

2. I put 10 mL of water into the tube. The weight was 10 g.

3. I took the water bath and set it to -15 degrees. I placed the test tube of water into the bath.

4. The water began to form ice at 0 degrees.

Experiment 2

1. I took an empty test tube and placed it on the balance.

2. I added 2 grams of FP sample 1.

3. The mass was 2 grams.

4. I added 10 mL of water.

5. The mass is now 12 g.

6. I placed the test tube in the bath.

7. Ice first began forming at -2.1.

8. I took another test tube and placed it on the balance.

9. I added 2 g of FP sample 2.

10. The mass is 2 g.

11. I added 10 mL of water.

12. Ice began to form on Sample 2 at -3.6.

We are given that the Van''t Hoff factor of Sample 1 is 1 and Sample 2 is 2.

Answer 1

Freezing point experiment

1. If we took 4 g sample instead of 2 g, the resulting freezing point lowering would be greater than that observed for 2 g sample.

2. molality = grams of solute/molar mas x kg of solvent

as density of water = 1 g/ml,

volume of water = mass of water

molality of NaCl solution = 154.286 g/58.44 g/mol x 2 kg = 1.32 m

3. molar mass of sample = grams of sample/freezing point of sample x kg of solvent

For sample 2

molar mass = 2/-3.6 x 0.01 = 55.55 g/mol