Textbook Question
A solution is 0.010 M in Ba2+ and 0.020 M in Ca2+. b. What is the remaining concentration of the cation that precipitates first, when the other cation begins to precipitate?
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Ch.17 - Aqueous Ionic Equilibrium
Chapter 17, Problem 111
Use the appropriate values of Ksp and Kf to find the equilibrium constant for the reaction. FeS(s) + 6 CN-(aq) ⇌ Fe(CN)64-(aq) + S2-(aq)
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Identify the relevant equilibrium reactions and their constants: The dissolution of FeS and the formation of the complex ion Fe(CN)_6^{4-}.
Write the dissolution reaction for FeS: FeS(s) \rightleftharpoons Fe^{2+}(aq) + S^{2-}(aq) with its solubility product constant K_{sp}.
Write the formation reaction for the complex ion: Fe^{2+}(aq) + 6 CN^-(aq) \rightleftharpoons Fe(CN)_6^{4-}(aq) with its formation constant K_f.
Combine the two reactions to obtain the overall reaction: FeS(s) + 6 CN^-(aq) \rightleftharpoons Fe(CN)_6^{4-}(aq) + S^{2-}(aq).
Calculate the equilibrium constant for the overall reaction by multiplying the K_{sp} of FeS and the K_f of Fe(CN)_6^{4-}.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solubility Product Constant (Ksp)
The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of sparingly soluble ionic compounds. It quantifies the extent to which a compound can dissolve in water, represented by the concentrations of its ions at equilibrium. For the reaction involving FeS, Ksp helps determine the solubility of FeS in the presence of complexing agents like CN-.
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Solubility Product Constant
Formation Constant (Kf)
The formation constant (Kf) is a measure of the stability of a complex ion in solution. It quantifies the equilibrium between the free ions and the complex formed when they react. In the given reaction, Kf is crucial for understanding how effectively CN- ions bind with Fe2+ to form the complex ion Fe(CN)64-, influencing the overall equilibrium of the reaction.
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02:20Complex Ions and Formation Constant
Equilibrium Constant (K)
The equilibrium constant (K) for a reaction is derived from the concentrations of the products and reactants at equilibrium. It provides insight into the extent of the reaction and can be calculated using Ksp and Kf values. In this case, the equilibrium constant for the reaction involving FeS and CN- can be determined by combining the Ksp of FeS and the Kf for the formation of the complex ion, reflecting the relationship between solubility and complexation.
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Related Practice
Open Question
A solution is 0.022 M in Fe2+ and 0.014 M in Mg2+. a. If potassium carbonate is used to selectively precipitate one of the cations while leaving the other cation in solution, which cation will precipitate first? What minimum concentration of K2CO3 will trigger the precipitation of the cation that precipitates first? b. What is the remaining concentration of the cation that precipitates first when the other cation begins to precipitate?
Textbook Question
A solution is made 1.1⨉10-3 M in Zn(NO3)2 and 0.150 M in NH3. After the solution reaches equilibrium, what concentration of Zn2+(aq) remains?
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Textbook Question
Use the appropriate values of Ksp and Kf to find the equilibrium constant for the reaction. PbCl2(s) + 3 OH-(aq) ⇌ Pb(OH)3-(aq) + 2 Cl-(aq)
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Open Question
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