CHEM 104 Module 3 | Q&A | 2026/2027 | General Chemistry II | Portage Learning

,CHEM 104 Module 3 | Q&A | 2026/2027 | General Chemistry II |
Portage Learning

1. What is the solubility product constant (Ksp) expression for BaF₂?

A) Ksp = [Ba²⁺][F⁻]

B) Ksp = [Ba²⁺][F⁻]²

C) Ksp = [Ba²⁺]²[F⁻]

D) Ksp = [BaF₂] / ([Ba²⁺][F⁻]²)



Correct Answer: Ksp = [Ba²⁺][F⁻]²



Rationale: BaF₂(s) ⇌ Ba²⁺(aq) + 2F⁻(aq). The Ksp expression is the product of
the ion concentrations, each raised to its stoichiometric coefficient: Ksp =
[Ba²⁺][F⁻]². The solid BaF₂ is not included because its concentration is
constant.



2. Calculate the molar solubility of BaF₂ if Ksp = 1.0 × 10⁻⁶.

A) 1.0 × 10⁻² M

B) 6.3 × 10⁻³ M

C) 1.0 × 10⁻⁶ M

D) 3.2 × 10⁻⁴ M



Correct Answer: 6.3 × 10⁻³ M



Rationale: Let s = molar solubility. BaF₂(s) ⇌ Ba²⁺ + 2F⁻ gives [Ba²⁺] = s and
[F⁻] = 2s. Ksp = (s)(2s)² = 4s³. s = (Ksp/4)^(1/3) = (1.0×10⁻⁶/4)^(1/3) =
6.3×10⁻³ M.

,3. Calculate the Ksp of MnS if the solubility of MnS is 0.0001375 g per 100
mL. Molar mass of MnS = 87.01 g/mol.

A) 1.80 × 10⁻¹⁰

B) 2.50 × 10⁻¹⁰

C) 1.58 × 10⁻⁵

D) 3.16 × 10⁻¹⁰



Correct Answer: 2.50 × 10⁻¹⁰



Rationale: Solubility in mol/L = (0.0001375 g / 0.100 L) / 87.01 g/mol =
1.580×10⁻⁵ M. For MnS(s) ⇌ Mn²⁺ + S²⁻, Ksp = s² = (1.580×10⁻⁵)² =
2.50×10⁻¹⁰.



4. For the salt AgCl, if the molar solubility is 1.34 × 10⁻⁵ M, what is the Ksp?

A) 1.8 × 10⁻¹⁰

B) 1.34 × 10⁻⁵

C) 1.8 × 10⁻⁵

D) 3.6 × 10⁻¹⁰



Correct Answer: 1.8 × 10⁻¹⁰



Rationale: AgCl(s) ⇌ Ag⁺ + Cl⁻, so [Ag⁺] = s and [Cl⁻] = s. Ksp = s² =
(1.34×10⁻⁵)² = 1.8×10⁻¹⁰.



5. What is the effect of adding NaF to a saturated solution of BaF₂?

A) The solubility of BaF₂ increases

B) The solubility of BaF₂ decreases

, C) The solubility of BaF₂ remains unchanged

D) BaF₂ precipitates completely



Correct Answer: The solubility of BaF₂ decreases



Rationale: Adding NaF introduces the common ion F⁻, which shifts the
equilibrium BaF₂(s) ⇌ Ba²⁺ + 2F⁻ to the left (toward the solid), decreasing
the solubility of BaF₂.



6. The common ion effect is best described as:

A) The decrease in solubility of a salt when a common ion is added

B) The increase in solubility of a salt when a common ion is added

C) The effect of temperature on solubility

D) The effect of pressure on gas solubility



Correct Answer: The decrease in solubility of a salt when a common ion is
added



Rationale: The common ion effect is the decrease in solubility of an ionic
compound when a common ion is added to the solution, due to Le Châtelier's
Principle shifting the equilibrium toward the solid.



7. Calculate the molar solubility of PbCl₂. Ksp of PbCl₂ = 1.7 × 10⁻⁵.

A) 1.7 × 10⁻⁵ M

B) 1.62 × 10⁻² M

C) 2.57 × 10⁻² M

D) 8.5 × 10⁻⁶ M