A solution is 0.022 M in Fe2+ and 0.014 M in Mg2+. a. If potassium carbonate is used to selectively precipitate one of the cations while leaving the other cation in solution, which cation will precipitate first? What minimum concentration of K2CO3 will trigger the precipitation of the cation that precipitates first? b. What is the remaining concentration of the cation that precipitates first when the other cation begins to precipitate?

Verified step by step guidance

1. Identify the solubility product constants (Ksp) for the carbonates of Fe2+ and Mg2+. These values are necessary to determine which cation will precipitate first.
2. Write the balanced chemical equations for the precipitation reactions: FeCO3(s) ⇌ Fe2+(aq) + CO3^2-(aq) and MgCO3(s) ⇌ Mg2+(aq) + CO3^2-(aq).
3. Use the Ksp expressions for each reaction: Ksp(FeCO3) = [Fe2+][CO3^2-] and Ksp(MgCO3) = [Mg2+][CO3^2-].
4. Calculate the ion product for each cation using the initial concentrations and compare them to their respective Ksp values to determine which cation will precipitate first. The cation with the ion product reaching its Ksp first will precipitate first.
5. Determine the minimum concentration of K2CO3 needed to reach the Ksp of the cation that precipitates first by solving for [CO3^2-] in the Ksp expression of that cation.