Chapter 18, Problem 92A

Interpretation Introduction

Interpretation: If the two ions in the solutions mix and cause precipitation, the concentration of the two ions is to be determined.

Concept introduction: Precipitation is a chemical process in which a solution is converted into a solid by changing the solute into insoluble or supersaturating the solution.

Answer to Problem 92A

For precipitation to occur when solutions of two ions are mixed, the concentrations of both ions must be higher than the solubility product constant Ksp for the compound produced.

Explanation of Solution

For a precipitate to be formed, the concentrations of the two ions present in the mixture must be higher than the solubility product constant $\left(K_{\text{sp}}\right)$ for the compound obtained from the mixture of the two ions. The solution has reached its maximum concentration of compound after precipitation and forming an insoluble compound.

If the concentrations of two ions in a mixture are less than the solubility product constant for a precipitated product, no precipitate is produced, and the solution is unsaturated.

Conclusion

For precipitation to occur when solutions of two ions are mixed, the concentrations of both ions must be higher than the solubility product constant Ksp for the compound produced.