Quick answer: The solubility product Ksp is the equilibrium constant for a sparingly soluble ionic solid dissolving, such as AgCl(s) ⇌ Ag⁺ + Cl⁻, with Ksp = [Ag⁺][Cl⁻]. This AP Chemistry worksheet on solubility product Ksp gives 20 problems from easy to hard: write the Ksp expressions, solubility of silver bromide and precipitate or not. The worked answers are on a separate page, and the worksheet is a free printable PDF.
These problems train Unit 7 of AP Chemistry: writing Ksp expressions, finding molar solubility, comparing Q with Ksp, and applying the common ion and pH effects. They also suit A Level and first-year university chemistry students.
Level 1 problems use direct substitution. Level 2 problems involve stoichiometry such as 4s³, mixing volumes and concentrations. The last five are level 3 problems on buffered solutions, separation and multi-step reasoning.
Level: AP Chemistry · Curriculum: AP Chem Unit 7
Problem 1 Write the Ksp expressions ★★★
Write the dissolving equation and the Ksp expression for (a) BaSO₄, (b) PbI₂, (c) Ag₃PO₄.Problem 2 Solubility of silver bromide ★★★
Aarav in Pune looks up Ksp(AgBr) = 5.4 × 10⁻¹³. Calculate the molar solubility.Problem 3 Precipitate or not ★★★
A mixture of Ag⁺ and Cl⁻ has Q = 3.0 × 10⁻⁹. Ksp(AgCl) = 1.8 × 10⁻¹⁰. Decide whether a precipitate forms.Problem 4 Ksp from mass solubility ★★★
Chiamaka in Lagos finds that 0.043 g of PbSO₄ (M = 303.3 g/mol) dissolves in 1.00 dm³ of water.1. Calculate s in mol/dm³.
2. Calculate Ksp.
Problem 5 Ksp of calcium carbonate ★★★
The molar solubility of CaCO₃ is 7.1 × 10⁻⁵ mol/dm³ (M = 100.1 g/mol).1. Calculate Ksp.
2. Calculate the mass that dissolves per dm³.
Problem 6 Which salts like acid? ★★★
Predict which salts dissolve better in dilute nitric acid than in water: AgCl, CaCO₃, BaSO₄, Mg(OH)₂.Problem 7 Lead(II) iodide ★★★
Ksp(PbI₂) = 9.8 × 10⁻⁹.1. Calculate the molar solubility.
2. Calculate [I⁻] in the saturated solution.
Problem 8 Silver chromate ★★★
Ksp(Ag₂CrO₄) = 1.1 × 10⁻¹². Calculate the molar solubility and [Ag⁺] in a saturated solution.Problem 9 Ksp of calcium hydroxide ★★★
Wanjiru in Nairobi measures the molar solubility of Ca(OH)₂ as 0.011 mol/dm³. Calculate Ksp and the pH of the saturated solution.Problem 10 Common ion effect ★★★
Calculate the molar solubility of AgCl in 0.050 mol/dm³ NaCl and compare it with its solubility in pure water.Problem 11 CaF₂ in fluoride solution ★★★
Calculate s for CaF₂ (Ksp = 3.5 × 10⁻¹¹) in 0.020 mol/dm³ NaF and compare it with pure water.Problem 12 Mixing two solutions ★★★
Diego in Texas mixes 100.0 cm³ of 2.0 × 10⁻⁴ mol/dm³ AgNO₃ with 100.0 cm³ of 4.0 × 10⁻⁴ mol/dm³ NaCl. Ksp(AgCl) = 1.8 × 10⁻¹⁰.2. Calculate Q.
3. Decide whether AgCl precipitates.
Problem 13 Magnesium hydroxide and acid ★★★
Explain, with equations, why Mg(OH)₂ dissolves when dilute hydrochloric acid is added.Problem 14 Which precipitates first? ★★★
A solution contains 0.010 mol/dm³ Cl⁻ and 0.010 mol/dm³ CrO₄²⁻. Solid AgNO₃ is added slowly (no volume change). Ksp(AgCl) = 1.8 × 10⁻¹⁰ and Ksp(Ag₂CrO₄) = 1.1 × 10⁻¹².1. Calculate [Ag⁺] needed to start precipitating AgCl.
2. Calculate [Ag⁺] needed to start precipitating Ag₂CrO₄.
3. State which solid forms first.
Problem 15 Barium sulfate in a drink ★★★
Emma in Leeds shakes excess BaSO₄ (Ksp = 1.1 × 10⁻¹⁰, M = 233.4 g/mol) with 500 cm³ of water. Calculate the mass that dissolves.Problem 16 Buffered magnesium hydroxide ★★★
Mg(OH)₂ has Ksp = 5.6 × 10⁻¹².1. Calculate s and the pH in pure water.
2. Calculate s in a buffer held at pH 10.00.
3. Explain the difference.
Problem 17 Separating by precipitation ★★★
Using the data of “Which precipitates first?”, Mei in Singapore keeps adding AgNO₃ until Ag₂CrO₄ just begins to precipitate.1. State [Ag⁺] at that moment.
2. Calculate [Cl⁻] remaining.
3. Calculate the percentage of Cl⁻ still in solution and say whether the separation is good.
Problem 18 Calcium fluoride precipitation ★★★
Kofi in Accra mixes 50.0 cm³ of 0.0040 mol/dm³ Ca(NO₃)₂ with 50.0 cm³ of 0.0010 mol/dm³ NaF. Ksp(CaF₂) = 3.5 × 10⁻¹¹.1. Calculate [Ca²⁺] and [F⁻] after mixing.
2. Calculate Q and decide whether CaF₂ precipitates.
3. Calculate the minimum [F⁻] needed to start precipitation at that [Ca²⁺].
Problem 19 Iron(III) hydroxide and pH ★★★
Fe(OH)₃ has Ksp = 2.8 × 10⁻³⁹. In a buffered solution Fe(OH)₃(s) ⇌ Fe³⁺ + 3OH⁻.1. Write the Ksp expression.
2. Calculate [Fe³⁺] at pH 7.00.
3. Calculate [Fe³⁺] at pH 3.00.
4. Explain why iron rusts out of water but stays dissolved in acidic mine water.
Problem 20 Error in the setup ★★★
A student calculates the molar solubility of Ag₂CrO₄ (Ksp = 1.1 × 10⁻¹²) as √Ksp = 1.0 × 10⁻⁶ mol/dm³.1. Identify the mistake.
2. Calculate the correct molar solubility.
3. Calculate by what factor the student’s value is wrong.
