General chemistryLesson 1 of 2 in the course Equilibria of Other Reaction Classes

Solubility Equilibria: Ksp, Precipitation, and Common-Ion Effects

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

A substance with finite solubility can form a saturated solution when the solvent contains as much dissolved solute as it can hold under the given conditions. If more solid is added, some remains undissolved, producing a heterogeneous mixture of solid and solution.

AgCl(s)⇌Ag+(aq)+Cl−(aq)AgCl(s) \rightleftharpoons Ag^+(aq)+Cl^-(aq)

Silver chloride dissolves to produce aqueous ions, while silver and chloride ions combine to form solid AgCl. The concentrations of dissolved ions remain constant at equilibrium even though both processes continue.

All flashcards

Molar solubility
Moles of a compound that dissolve per liter of saturated solution.
Ion product, Qsp
The concentration product calculated using the Ksp expression and current ion concentrations.
Common-ion effect
Reduced solubility caused by adding an ion already present in the dissolution equilibrium.
Selective precipitation
Separating ions by precipitating their compounds at different counter-ion concentrations.
Precipitation threshold
The ion concentration at which the ion product reaches the solubility product.

Quiz questions

  1. For a sparingly soluble salt, what does Qsp > Ksp indicate?Answer: Precipitation is favored until the ion product decreases.
  2. Equal volumes of 2.0 × 10⁻⁴ M AgNO₃ and 2.0 × 10⁻⁴ M NaCl are mixed. Before any precipitation, what is the concentration of each relevant ion?Answer: 1.0 × 10⁻⁴ M Ag⁺ and 1.0 × 10⁻⁴ M Cl⁻
  3. For CaF₂ dissolving in pure water with molar solubility s, what is the fluoride concentration?Answer: [F⁻] = 2s
  4. For M(OH)₂(s) ⇌ M²⁺ + 2OH⁻, what hydroxide concentration corresponds to a specified [M²⁺] at saturation?Answer: [OH⁻] = √(Ksp/[M²⁺])
  5. When comparing two possible precipitates, what determines which forms first as a counter-ion is added?Answer: Which precipitation threshold is reached at the lower counter-ion concentration.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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