Chemistry 2e · 15.3 Coupled Equilibria

Coupled Equilibria: practice problems

10 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

1. Exercises 86

   Calculate the equilibrium concentration of Ni²⁺ in a 1.0-M solution [Ni(NH₃)₆](NO₃)₂.

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2. Exercises 88

   Calculate the equilibrium concentration of Cu²⁺ in a solution initially with 0.050 M Cu²⁺ and 1.00 M NH₃.

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3. Exercises 90

   Calculate the Fe³⁺ equilibrium concentration when 0.0888 mole of K₃[Fe(CN)₆] is added to a solution with 0.00010 M CN–.

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4. Exercises 93

   Calculate the molar solubility of Al(OH)₃ in a buffer solution with 0.100 M NH₃ and 0.400 M ${\text{NH}}_4{}^{+}.$

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5. Exercises 95

   What is the molar solubility of BaSO₄ in a 0.250-M solution of NaHSO₄? K${}_a$ for ${\text{HSO}}_4{}^{\text{-}}$ = 1.2 $\times$ 10–2.

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6. Exercises 97

   What is the molar solubility of Pb(OH)₂ in a 0.138-M solution of CH₃NH₂?

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7. Exercises 99

   A 0.125-M solution of Mn(NO₃)₂ is saturated with H₂S ([H₂S] = 0.10 M). At what pH does MnS begin to precipitate?

   $\text{MnS}(s)\rightleftharpoons {\text{Mn}}^{\text{2+}}(aq)+{\text{S}}^{\text{2-}}(aq)K_{\text{sp}}=2.3\times {10}^{\text{-13}}$

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8. Exercises 101

   The following question is taken from a Chemistry Advanced Placement Examination and is used with the permission of the Educational Testing Service.

   Solve the following problem:

   ${\text{MgF}}_2(s)\rightleftharpoons {\text{Mg}}^{\text{2+}}(aq)+2{\text{F}}^{\text{-}}(aq)$

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9. Exercises 103

   Which of the following compounds, when dissolved in a 0.01-M solution of HClO₄, has a solubility greater than in pure water: AgBr, BaF₂, Ca₃(PO₄)₂, ZnS, PbI₂? Explain your answer.

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10. Exercises 105

    What is the effect on the amount of CaHPO₄ that dissolves and the concentrations of Ca²⁺ and ${\text{HPO}}_4{}^{\text{2-}}$ when each of the following are added to a mixture of solid CaHPO₄ and water at equilibrium?

    (a) CaCl₂

    (b) HCl

    (c) KClO₄

    (d) NaOH

    (e) CaHPO₄

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