Final answer:
The correct answer is b. Ksp is equal to the solubility product. This is because when potassium sulfate is added to the saturated calcium sulfate solution, the reaction quotient exceeds Ksp, causing CaSO4 to precipitate until equilibrium is reestablished, at which point Q is again equal to Ksp.
Step-by-step explanation:
When a solution of potassium sulfate is added to a saturated solution of calcium sulfate, precipitation of calcium sulfate occurs. The solubility product constant (Ksp) is crucial to understanding why this happens. When additional sulfate ions are introduced by the potassium sulfate solution, the reaction quotient (Q) becomes greater than the Ksp, causing CaSO4 to precipitate. At this point, b. Ksp is equal to the solubility product of calcium sulfate.
This is consistent with Le Chatelier's principle, which describes how the equilibrium will shift to mitigate the change caused by the excess sulfate ions. Precipitation occurs until the concentrations adjust so that Q equals Ksp again, meaning the system is at equilibrium and no more precipitation occurs unless the concentrations change again. Therefore, the answer to the question is b. Ksp is equal to the solubility product.