Chapter 17, Problem 17.16QP

Solubility Equilibria

Consider three hypothetical ionic solids: AX, AX₂, and AX₃ (each X forms X⁻). Each of these solids has the same K_sp value, 5.5 × 10 ⁷. You place 0.25 mol of each compound in a separate container and add enough water to bring the volume to 1.0 L in each case.

1. a Write the chemical equation for each of the solids dissolving in water.
2. b Would you expect the concentration of each solution to be 0.25 M in the compound? Explain, in some detail, why or why not.
3. c Would you expect the concentrations of the A cations (A⁺, A²⁺, and A³⁺) in the three solutions to be the same? Does just knowing the stoichiometry of each reaction help you determine the answer, or do you need something else? Explain your answer in detail, but without doing any arithmetic calculations.
4. d Of the three solids, which one would you expect to have the greatest molar solubility? Explain in detail, but without doing any arithmetic calculations.
5. e Calculate the molar solubility of each compound.