Why does adding a common ion to a saturated solution of a sparingly soluble salt increase the chance of precipitation?
Answer and explanation
Correct answer: Ionic product may increase beyond the limit
A saturated solution initially has Q equal to Ksp. Adding a common ion increases the concentration of one of the ions, so the ionic product Q rises and can become greater than Ksp. The excess ions then combine to form solid salt until equilibrium is restored. This is the common-ion effect. Ksp itself remains fixed at a given temperature; it does not become infinite.
Frequently asked questions
What is the correct answer to this question?
Ionic product may increase beyond the limit
Why is this the correct answer?
A saturated solution initially has Q equal to Ksp. Adding a common ion increases the concentration of one of the ions, so the ionic product Q rises and can become greater than Ksp. The excess ions then combine to form solid salt until equilibrium is restored. This is the common-ion effect. Ksp itself remains fixed at a given temperature; it does not become infinite.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Equilibrium. Topic: Solubility product and common ion effect.
