Wrap-Up

Well, that brings us to the end of the lesson; and, as usual, you should take some time to review the lesson, go back over the objectives and make sure that you can do all of the things that are indicated as being necessary for an adequate understanding of solutions. You can use the Self Quiz to verify this.

Self Quiz

Select the best answer for each of the questions below.

Which of the following should be least soluble in water?

a. Ba(NO3)2

b. NaCl

c. CH3OH

d. H2O2

e. O2

2. A white solid is poured into a beaker of water and stirred. The resulting material is a clear, colorless, homogeneous liquid. That material is a(n):

a. unsaturated solution.

b. saturated solution.

c. supersaturated solution.

d. colloidal dispersion.

e. suspension.

3. Calculate the heat of solution given the following information. When 2.0 g of a chemical (formula mass = 40 g/mole) is dissolved in 60.0 g of water the temperature of the water goes up 8.0°C.

4. Given the following solubility rules, how soluble is ZnSO4?

I. The sulfates of all metals are soluble except those of Pb2+, Hg+, Ba2+, and Ca2+. Silver sulfate is slightly soluble.

II. The sulfides of all metals are insoluble except those of the alkali metals and NH4+.

a. soluble

b. slightly soluble

c. insoluble

5. Refer to the solubility rules above. Will a precipitate form when a solution containing Na+ and S2- is mixed with a solution containing Zn2+ and NO3-?

a. yes

b. no

6. The freezing point of a BaCl2 solution should be _____ that of an equally concentrated NaCl solution.

a. higher than

b. lower than

c. the same as

7. What will happen in an osmosis apparatus containing water on the left side of a semipermeable membrane and sugar water on the right?

a. Water molecules will move to the right.

b. Water molecules will move to the left.

c. Sugar molecules will move to the right.

d. Sugar molecules will move to the left.

8. A chemical which partially dissociates into ions when it dissolves in water is a:

a. nonelectrolyte

b. weak electrolyte

c. strong electrolyte

10. Write an equation representing NiCl3 dissolving in water.

Self Quiz Answers

Select the best answer for each of the questions below.

Which of the following should be least soluble in water?

a. Ba(NO3)2

b. NaCl

c. CH3OH

d. H2O2

e. O2

Water is very polar, so the least soluble substance here will be the non-polar O2

2. A white solid is poured into a beaker of water and stirred. The resulting material is a clear, colorless, homogeneous liquid. That material is a(n):

a. unsaturated solution.

b. saturated solution.

c. supersaturated solution.

d. colloidal dispersion.

e. suspension.

Based on the information given, it could be either saturated or unsaturated, but to be saturated you would have to have added exactly enough solute to reach the solubility limit, which is vanishingly unlikely. It is not a colloidal dispersion or suspension because it is clear and homogeneous.

3. Calculate the heat of solution given the following information. When 2.0 g of a chemical (formula mass = 40 g/mole) is dissolved in 60.0 g of water the temperature of the water goes up 8.0°C.

60.0 g * 4.184 J/g°C * 8.0 °C = 2008 J

2.0 g/40 g/mol = 0.05 mol

ΔHsol = 2008 J/0.05 mol = 40160 J/mol = 40.16 kJ/mol

4. Given the following solubility rules, how soluble is ZnSO4?

I. The sulfates of all metals are soluble except those of Pb2+, Hg+, Ba2+, and Ca2+. Silver sulfate is slightly soluble.

II. The sulfides of all metals are insoluble except those of the alkali metals and NH4+.

a. soluble

b. slightly soluble

c. insoluble

This is zinc sulfate not zinc sulfide, so it is soluble

5. Refer to the solubility rules above. Will a precipitate form when a solution containing Na+ and S2- is mixed with a solution containing Zn2+ and NO3-?

a. yes

b. no

Yes. The precipitate would be ZnS, forming according to the equation below

Zn(NO3)2 (aq) + Na2S (aq) → ZnS (s) + 2 NaNO3 (aq)

6. The freezing point of a BaCl2 solution should be _____ that of an equally concentrated NaCl solution.

a. higher than

b. lower than

c. the same as

Barium chloride dissociates into three ions whereas sodium chloride dissociates into two. Thus, the barium chloride solution contains more particles, so the amount of freezing point depression (a colligative property) is increased

7. What will happen in an osmosis apparatus containing water on the left side of a semipermeable membrane and sugar water on the right?

a. Water molecules will move to the right.

b. Water molecules will move to the left.

c. Sugar molecules will move to the right.

d. Sugar molecules will move to the left.

Sugar molecules cannot cross the membrane. Water molecules will move toward the more concentrated solution.

8. A chemical which partially dissociates into ions when it dissolves in water is a:

a. nonelectrolyte

b. weak electrolyte

c. strong electrolyte

This is the definition of a weak electrolyte

9. Write an equation representing NiCl3 dissolving in water.

NiCl3 (s) → Ni3+ (aq) + 3 Cl- (aq)

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