Solubility product Ksp lab answers, AP Chemistry (PDF)

The method and the results are on the solubility product Ksp lab. Do the analysis yourself first, then check the answers below.

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⁻]. These answers go with the AP Chemistry lab on solubility product Ksp: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.

Solubility product Ksp lab answers for AP Chemistry (free PDF download)

Here are the solubility product Ksp lab answers for AP Chemistry: graph, calculations, uncertainties and conclusion. First do the lab yourself, then compare, and go back to the lesson if needed.

The sample data are used for every answer. Your own results will depend on the temperature and on how long the solution stood. Compare your value of Ksp with the accepted one and comment on the sources of error.

Level: AP Chemistry · Curriculum: AP Chem Unit 7

Contents

Solubility product Ksp lab answers: the analysis explained

Question 1 Mean titre

(11.3 + 11.2 + 11.4) / 3 = 11.3 cm³.

Question 2 Amount of hydroxide

n(HCl) = 0.0113 × 0.0500 = 5.650 × 10⁻⁴ mol, so n(OH⁻) = 5.650 × 10⁻⁴ mol.

Question 3 Hydroxide concentration

[OH⁻] = 5.650 × 10⁻⁴ / 0.0250 = 0.0226 mol/dm³.

Question 4 Molar solubility

Each Ca(OH)₂ releases two OH⁻, so s = [Ca²⁺] = 0.0226 / 2 = 0.0113 mol/dm³.

Question 5 Calculate Ksp

Ksp = [Ca²⁺][OH⁻]² = 0.0113 × 0.0226² = 5.77 × 10⁻⁶.

Question 6 Percentage difference

Difference = (5.77 × 10⁻⁶ − 5.0 × 10⁻⁶) / 5.0 × 10⁻⁶ × 100 = 15 %, a reasonable agreement for a school lab.

Question 7 Source of error

Carbon dioxide from the air reacts with dissolved Ca(OH)₂ to form insoluble CaCO₃, lowering [OH⁻]. Keep the beaker covered and titrate soon after filtering.