AP Chemistry Practice Quiz: Introduction to Solubility Equilibria

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 11 questions to check your progress.

Question 1 of 11

The dissolution of a salt in water is a reversible process. The extent to which this process occurs is described by what constant?

A)Ka, the acid-dissociation constantB)Kb, the base-dissociation constantC)Ksp, the solubility-product constantD)Kw, the ion-product constant for water

All Questions (11)

The dissolution of a salt in water is a reversible process. The extent to which this process occurs is described by what constant?

A) Ka, the acid-dissociation constant

B) Kb, the base-dissociation constant

C) Ksp, the solubility-product constant

D) Kw, the ion-product constant for water

Correct Answer: C

The provided content states that 'The dissolution of a salt is a reversible process whose extent can be described by Ksp, the solubility-product constant.'

According to the quantitative relationship between solubility rules and the solubility-product constant, a salt that is classified as 'soluble' would be expected to have what characteristic?

A) A Ksp value less than 1

B) A Ksp value equal to 1

C) A Ksp value greater than 1

D) A Ksp value of zero

Correct Answer: C

The content explicitly states that 'Ksp values > 1 correspond to soluble salts', providing a quantitative link to the general solubility rules.

The Ksp for silver chloride, AgCl, is 1.8 x 10⁻¹⁰. What is the molar solubility (s) of AgCl in pure water? The dissolution equation is AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq).

A) s = √(1.8 x 10⁻¹⁰)

B) s = 1.8 x 10⁻¹⁰

C) s = (1.8 x 10⁻¹⁰)²

D) s = ³√(1.8 x 10⁻¹⁰)

Correct Answer: A

For the dissolution AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), the Ksp expression is Ksp = [Ag⁺][Cl⁻]. If the molar solubility is 's', then [Ag⁺] = s and [Cl⁻] = s. Therefore, Ksp = (s)(s) = s². To find the solubility 's', you must calculate the square root of Ksp.

A saturated solution of lead(II) sulfate, PbSO₄, is found to have a molar solubility of 1.4 x 10⁻⁴ M. What is the value of Ksp for PbSO₄?

A) 1.4 x 10⁻⁴

B) 2.8 x 10⁻⁴

C) 2.0 x 10⁻⁸

D) 4.0 x 10⁻¹⁶

Correct Answer: C

The dissolution is PbSO₄(s) ⇌ Pb²⁺(aq) + SO₄²⁻(aq). If the molar solubility is s = 1.4 x 10⁻⁴ M, then [Pb²⁺] = s and [SO₄²⁻] = s. The Ksp is calculated as Ksp = [Pb²⁺][SO₄²⁻] = (s)(s) = s² = (1.4 x 10⁻⁴)² = 1.96 x 10⁻⁸, which is approximately 2.0 x 10⁻⁸.

The molar solubility of calcium fluoride, CaF₂, in a saturated solution is determined to be 's' M. What is the correct expression for the Ksp of CaF₂?

A) Ksp = s²

B) Ksp = 2s²

C) Ksp = 4s²

D) Ksp = 4s³

Correct Answer: D

The dissolution equation is CaF₂(s) ⇌ Ca²⁺(aq) + 2F⁻(aq). If the molar solubility is 's', then [Ca²⁺] = s and [F⁻] = 2s. The Ksp expression is Ksp = [Ca²⁺][F⁻]² = (s)(2s)² = (s)(4s²) = 4s³. This calculation is based on using the molar solubility of species in a saturated solution to calculate Ksp.

Consider the following salts and their Ksp values: BaSO₄, Ksp = 1.1 x 10⁻¹⁰ CuS, Ksp = 6.0 x 10⁻³⁷ PbS, Ksp = 3.0 x 10⁻²⁸ Based on this information, which salt is the least soluble in water?

A) BaSO₄

B) CuS

C) PbS

D) Their solubilities cannot be compared.

Correct Answer: B

All three salts dissociate into two ions (a 1:1 ratio). For salts with the same ion ratio, a smaller Ksp value corresponds to lower molar solubility. This relationship can be used to predict the relative solubility. Since CuS has the smallest Ksp (6.0 x 10⁻³⁷), it is the least soluble.

The Ksp for lead(II) chloride, PbCl₂, is 1.7 x 10⁻⁵. Which expression correctly calculates its molar solubility (s)? The dissolution is PbCl₂(s) ⇌ Pb²⁺(aq) + 2Cl⁻(aq).

A) s = √(1.7 x 10⁻⁵)

B) s = ³√(1.7 x 10⁻⁵)

C) s = ³√((1.7 x 10⁻⁵)/4)

D) s = ³√((1.7 x 10⁻⁵)/2)

Correct Answer: C

For the dissolution PbCl₂(s) ⇌ Pb²⁺(aq) + 2Cl⁻(aq), the Ksp expression is Ksp = [Pb²⁺][Cl⁻]². If the molar solubility is 's', then [Pb²⁺] = s and [Cl⁻] = 2s. Substituting these into the expression gives Ksp = (s)(2s)² = 4s³. To solve for s, the equation is rearranged: s³ = Ksp/4, so s = ³√(Ksp/4).

The establishment of a solubility equilibrium for a salt, as described by Ksp, implies that the solution is in what state?

A) Unsaturated, where more salt can dissolve

B) Saturated, where the rate of dissolution equals the rate of precipitation

C) Supersaturated, containing more solute than an equilibrium solution

D) Dilute, containing a very small amount of salt

Correct Answer: B

The Ksp describes the equilibrium condition for the reversible process of a salt dissolving. This equilibrium exists in a saturated solution, where the dissolved ions are in equilibrium with the undissolved solid.

What fundamental relationship allows for the calculation of a substance's solubility from its Ksp value?

A) The Ksp is directly equal to the molar solubility.

B) The Ksp is an equilibrium constant that relates the concentrations of the dissolved ions in a saturated solution.

C) The Ksp value is only used to determine if a salt is 'soluble' or 'insoluble'.

D) The Ksp is inversely proportional to the temperature of the solution.

Correct Answer: B

The Ksp is the solubility-product constant, which is the equilibrium constant for the dissolution process. By setting up the equilibrium expression (Ksp = [ion1]^x[ion2]^y) and relating the ion concentrations to the molar solubility (s), one can solve for 's'. This is the core relationship used for the calculation.

Given AgCl (Ksp = 1.8 x 10⁻¹⁰) and Ag₂CrO₄ (Ksp = 1.1 x 10⁻¹²). Which statement correctly compares their molar solubilities?

A) AgCl is more soluble because its Ksp is larger.

B) Ag₂CrO₄ is more soluble because its Ksp is smaller.

C) A direct comparison of Ksp values is misleading; the molar solubility of each must be calculated to determine which is more soluble.

D) They have the same molar solubility because they both contain silver ions.

Correct Answer: C

The content states that Ksp can be used to predict relative solubility. However, a direct comparison of Ksp values is only valid for salts with the same ion ratio. AgCl dissociates into 2 ions (Ag⁺, Cl⁻), while Ag₂CrO₄ dissociates into 3 ions (2Ag⁺, CrO₄²⁻). To compare their solubilities, one must first calculate the molar solubility (s) for each. A simple comparison of Ksp values is not sufficient.

In a saturated solution of iron(III) hydroxide, Fe(OH)₃, the concentration of Fe³⁺(aq) is found to be 's' M. What is the correct expression for the Ksp of Fe(OH)₃?

A) Ksp = s⁴

B) Ksp = 9s⁴

C) Ksp = 27s³

D) Ksp = 27s⁴

Correct Answer: D

The dissolution equation is Fe(OH)₃(s) ⇌ Fe³⁺(aq) + 3OH⁻(aq). If the molar solubility of Fe(OH)₃ is 's', then the equilibrium concentration of [Fe³⁺] is 's' and the equilibrium concentration of [OH⁻] is '3s'. The Ksp expression is Ksp = [Fe³⁺][OH⁻]³. Substituting the concentrations in terms of 's' gives Ksp = (s)(3s)³ = (s)(27s³) = 27s⁴.