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title: "A student investigates the common-ion effect on the dissolution of lead(II) iodide by preparing saturated solutions under two conditions at \\(25^\\circ\\text{C}\\):  Condition 1: \\(\\text{PbI}_2(s)\\) dissolved in pure distilled water  Condition 2: \\(\\text{PbI}_2(s)\\) dissolved in \\(0.10\\text{ M KI}(aq)\\)  The dissolution equilibrium and its solubility product constant at \\(25^\\circ\\text{C}\\) are given below. \\[\\text{PbI}_2(s) \\rightleftharpoons \\text{Pb}^{2+}(aq) + 2\\,\\text{I}^-(aq) \\quad K_{sp} = 4.0 \\times 10^{-9}\\]  Assuming that the added \\(0.10\\text{ M KI}(aq)\\) provides the predominant source of \\(\\text{I}^-(aq)\\) in Condition 2, what is the value of the ratio of the molar solubility of \\(\\text{PbI}_2\\) in pure water (\\(s_1\\)) to its molar solubility in \\(0.10\\text{ M KI}(aq)\\) (\\(s_2\\)), expressed as \\(\\dfrac{s_1}{s_2}\\)?"
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url: "https://nerd-notes.com/ubq/123833/"
date_modified: "2026-09-28T12:30:29+00:00"
---

# A student investigates the common-ion effect on the dissolution of lead(II) iodide by preparing saturated solutions under two conditions at \(25^\circ\text{C}\):

Condition 1: \(\text{PbI}_2(s)\) dissolved in pure distilled water

Condition 2: \(\text{PbI}_2(s)\) dissolved in \(0.10\text{ M KI}(aq)\)

The dissolution equilibrium and its solubility product constant at \(25^\circ\text{C}\) are given below.
\[\text{PbI}_2(s) \rightleftharpoons \text{Pb}^{2+}(aq) + 2\,\text{I}^-(aq) \quad K_{sp} = 4.0 \times 10^{-9}\]

Assuming that the added \(0.10\text{ M KI}(aq)\) provides the predominant source of \(\text{I}^-(aq)\) in Condition 2, what is the value of the ratio of the molar solubility of \(\text{PbI}_2\) in pure water (\(s_1\)) to its molar solubility in \(0.10\text{ M KI}(aq)\) (\(s_2\)), expressed as \(\dfrac{s_1}{s_2}\)?

A student investigates the common-ion effect on the dissolution of lead(II) iodide by preparing saturated solutions under two conditions at \(25^\circ\text{C}\):

Condition 1: \(\text{PbI}_2(s)\) dissolved in pure distilled water

Condition 2: \(\text{PbI}_2(s)\) dissolved in \(0.10\text{ M KI}(aq)\)

The dissolution equilibrium and its solubility product constant at \(25^\circ\text{C}\) are given below.
\[\text{PbI}_2(s) \rightleftharpoons \text{Pb}^{2+}(aq) + 2\,\text{I}^-(aq) \quad K_{sp} = 4.0 \times 10^{-9}\]

Assuming that the added \(0.10\text{ M KI}(aq)\) provides the predominant source of \(\text{I}^-(aq)\) in Condition 2, what is the value of the ratio of the molar solubility of \(\text{PbI}_2\) in pure water (\(s_1\)) to its molar solubility in \(0.10\text{ M KI}(aq)\) (\(s_2\)), expressed as \(\dfrac{s_1}{s_2}\)?

- **A.** \(4.0 \times 10^{-4}\)
- **B.** \(2.5 \times 10^1\)
- **C.** \(2.5 \times 10^2\)
- **D.** \(2.5 \times 10^3\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123833/*