A saturated solution of CaSO4(aq) is made in a beaker until there is excess calcium sulfate resting at the bottom. Then solid potassium sulfate is added. Which of the following is true? (The Ksp for potassium sulfate is larger than the Ksp for calcium sulfate)
a. More calcium sulfate will start to precipitate out of solution
b. More calcium sulfate will start to dissolve in solution
*I know that when a smaller Ksp is added to a bigger Ksp it precipitates out of solution. Is that the same in the reverse?*
I answered this at the original post. If that wasn't the same student let me know and I will try to find it and post a link to it.
In order to determine what will happen when solid potassium sulfate is added to a saturated solution of calcium sulfate (CaSO4), we need to compare the solubility product constants (Ksp) of both compounds. The solubility product constant is a measure of a substance's solubility in water.
According to the information given, the Ksp for potassium sulfate (K2SO4) is larger than the Ksp for calcium sulfate (CaSO4). This means that potassium sulfate is more soluble in water than calcium sulfate. When a compound with a larger Ksp is added to a solution containing a compound with a smaller Ksp, there is a likelihood of precipitation occurring.
Based on this, the correct answer is a. More calcium sulfate will start to precipitate out of solution. When solid potassium sulfate is added to the saturated solution of calcium sulfate, the potassium sulfate will dissolve, but the addition of the soluble potassium sulfate will cause the solubility equilibrium of calcium sulfate to shift toward the solid form, leading to precipitation of calcium sulfate.
To summarize, when a soluble compound with a larger Ksp is introduced to a solution containing a less soluble compound, it is likely to cause the less soluble compound to precipitate out of the solution.