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15.3 Coupled Equilibria

Systems where two or more equilibria share a species, so complexation or pH shifts solubility, and the combined constants used to find concentrations.

Chemistry 2e, 15.3 Coupled Equilibria

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10 exercises

15.3 Exercise 2

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

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15.3 Exercise 4

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

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15.3 Exercise 6

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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15.3 Exercise 9

Calculate the molar solubility of Al(OH)3 in a buffer solution with 0.100 M NH3 and 0.400 M NH4+.\text{NH}_{4} ^{+} .

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15.3 Exercise 11

What is the molar solubility of BaSO4 in a 0.250-M solution of NaHSO4? Ka for HSO4−\text{HSO}_{4} ^{−} = 1.2 ×\times 10–2.

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15.3 Exercise 13

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

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15.3 Exercise 15

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?

MnS(s)⇌Mn2+(aq)+S2−(aq) Ksp=2.3×10−13\text{MnS} \left(s\right) \rightleftharpoons \text{Mn}^{\text{2}+} \left(a q\right) + \text{S}^{\text{2}−} \left(a q\right) K_{\text{sp}} = 2.3 \times 10^{−\text{13}}

H2S(aq)+2H2O(l)⇌2H3O+(aq)+S2−(aq)K=1.0×10−26\text{H}_{2} \text{S} \left(a q\right) + 2 \text{H}_{2} \text{O} \left(l\right) \rightleftharpoons 2 \text{H}_{3} \text{O}^{+} \left(a q\right) + \text{S}^{\text{2}−} \left(a q\right) K = 1.0 \times 10^{−\text{26}}

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15.3 Exercise 17

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:

MgF2(s)⇌Mg2+(aq)+2F−(aq)\text{MgF}_{2} \left(s\right) \rightleftharpoons \text{Mg}^{\text{2}+} \left(a q\right) + 2 \text{F}^{−} \left(a q\right)

In a saturated solution of MgF2 at 18 °C, the concentration of Mg2+ is 1.21 ×\times 10–3 M. The equilibrium is represented by the preceding equation.

(a) Write the expression for the solubility-product constant, Ksp, and calcul…

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15.3 Exercise 19

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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15.3 Exercise 21

What is the effect on the amount of CaHPO4 that dissolves and the concentrations of Ca2+ and HPO42−\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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Adapted from General Chemistry © 2019 Rice University. Licensed under CC BY 4.0. Sources: Chemistry 2e, Chemistry: Atoms First 2e. Imported at revision 32c7196.