AP Chemistry · Topic 7.11

Introduction to Solubility Equilibria Practice

Part of Equilibrium.(SPQ-5.A)

Practice questions

12

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Sample questions

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  1. Sample 1difficulty 2/5

    For PbCl₂ ⇌ Pb²⁺ + 2 Cl⁻, K_sp =

    • A

      [Pb²⁺]²[Cl⁻]

    • B

      [PbCl₂]/[Pb²⁺][Cl⁻]

    • C

      [Pb²⁺][Cl⁻]²

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    • D

      [Pb²⁺][Cl⁻]

    Why

    Solid omitted; product of ion concentrations to coefficients.

  2. Sample 2difficulty 2/5

    A saturated solution in contact with undissolved solute is

    • A

      Not at equilibrium

    • B

      Subsaturated

    • C

      Pure solute

    • D

      At dissolution-precipitation equilibrium

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    Why

    Saturation = dynamic equilibrium between dissolved and solid phases.

  3. Sample 3difficulty 2/5

    A saturated solution of AgCl gives [Ag⁺] = 1.3×10⁻⁵ M.

    AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq) [Ag⁺]=[Cl⁻]=1.3×10⁻⁵ M Find Ksp

    What is Ksp of AgCl?

    • A

      1.7×10⁻⁵

    • B

      1.7×10⁻¹⁰

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    • C

      1.3×10⁻⁵

    • D

      2.6×10⁻⁵

    Why

    Ksp = [Ag⁺][Cl⁻] = (1.3×10⁻⁵)² = 1.69×10⁻¹⁰ ≈ 1.7×10⁻¹⁰.

  4. Sample 4difficulty 3/5

    Ksp(PbI2) = 7.1e-9.

    PbI2(s) <-> Pb2+ + 2 I- Ksp = [Pb2+][I-]^2 if solubility = s, [Pb2+] = s, [I-] = 2s Ksp = 4 s^3

    What is the molar solubility s in pure water (approximately)?

    • A

      7.1e-9 M

    • B

      2.7e-3 M

    • C

      8.4e-5 M

    • D

      1.2e-3 M

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    Why

    s^3 = Ksp/4 = 1.78e-9; s = cube root ~ 1.2e-3 M.

  5. Sample 5difficulty 3/5

    The Ksp values above are tabulated at 25 C in pure water.

    Salt Ksp AgCl 1.8e-10 AgBr 5.0e-13 AgI 8.5e-17 PbI2 7.1e-9

    Which silver halide is least soluble in pure water?

    • A

      All have equal molar solubility

    • B

      AgI

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    • C

      AgBr

    • D

      AgCl

    Why

    Among the 1:1 salts (AgX), the smallest Ksp gives the smallest molar solubility. AgI has Ksp = 8.5e-17, the smallest.