교과서 질문
Calculate the solubility of CuX in a solution that is 0.150 M in NaCN. Ksp for CuX is 1.27⨉10-36.
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18. Aqueous Equilibrium
Complex Ions: Formation Constant
객관식
Which of the following best explains why the formation of complex ions can increase the solubility of otherwise insoluble compounds?
A
Complex ion formation decreases the temperature required for dissolution.
B
Complex ion formation increases the lattice energy of the solid, making it easier to dissolve.
C
Complex ion formation reduces the concentration of free metal ions, shifting the equilibrium to dissolve more solid.
D
Complex ion formation neutralizes the anions in solution, preventing precipitation.
검증된 단계별 안내1
Understand the concept of solubility equilibrium for an ionic solid, which can be represented as: \(\text{Solid} \rightleftharpoons \text{Metal}^{n+} + \text{Anions}\), where the dissolution is governed by the solubility product constant, \(K_{sp}\).
Recognize that the formation of complex ions involves the metal ion reacting with ligands in solution to form a complex ion, for example: \(\text{Metal}^{n+} + \text{Ligand} \rightleftharpoons \text{Complex Ion}\), which has its own equilibrium constant, the formation constant \(K_f\).
Apply Le Ch\^atelier's principle: when complex ions form, they reduce the concentration of free metal ions in solution because metal ions are tied up in complexes.
Since the concentration of free metal ions decreases, the dissolution equilibrium shifts to the right to dissolve more solid to re-establish equilibrium, effectively increasing solubility.
Conclude that the key reason complex ion formation increases solubility is by reducing free metal ion concentration, not by changing lattice energy, temperature, or neutralizing anions.
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