Simultaneous Equilibria
Mediumchemistry
In a solution containing both AgCl and AgBr, if Ksp(AgCl) = 10⁻¹⁰ and Ksp(AgBr) = 10⁻¹³, which compound will precipitate first when Ag⁺ ions are added?
Select the correct option:
Solution
Incorrect! Answer:
AgBr
- Precipitation Condition: For a salt XY to precipitate, the ionic product must exceed the solubility product (I.P.≥Ksp).
- Analysis: Assume equal concentrations of Cl− and Br−.
- To precipitate AgCl, [Ag+]≥[Cl−]10−10
- To precipitate AgBr, [Ag+]≥[Br−]10−13
- Conclusion: Since 10−13 is a much smaller requirement for [Ag+] than 10−10, the concentration of silver ions will reach the saturation point of AgBr first.
- The salt with the lower Ksp (for identical stoichiometry) precipitates first.
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About This Question
- Subject
- chemistry
- Chapter
- equilibrium
- Topic
- simultaneous equilibria
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
AgBr
- Precipitation Condition: For a salt XY to precipitate, the ionic product must exceed the solubility product (I.P.≥Ksp).
- Analysis: Assume equal concentrations of Cl− and Br−.
- To precipitate AgCl, [Ag+]≥[Cl−]10−10
- To precipitate AgBr, [Ag+]≥[Br−]10−13
- Conclusion: Since 10−13 is a much smaller requirement for [Ag+] than 10−10, the concentration of silver ions will reach the saturation point of AgBr first.
- The salt with the lower Ksp (for identical stoichiometry) precipitates first.
This medium difficulty chemistry question is from the chapter equilibrium, covering the topic of simultaneous equilibria. It appeared in the 2025 exam.
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