A solution contains 0.010 M Ba²⁺ and 0.010 M Sr²⁺. The chemist wishes to precipitate nearly all of the barium ions as BaSO₄ while leaving most of the strontium ions in solution.
Solubility‐product data, 25 °C:
BaSO₄ Ksp=1.1×10−10
SrSO₄ Ksp=3.2×10−7
(a) Write the Ksp expressions for the dissolution of BaSO₄(s) and SrSO₄(s).
(b) Calculate the minimum sulfate ion concentration that will reduce [Ba2+] to 1.0 × 10⁻⁴ M.
(c) At the sulfate ion concentration determined in part (b), calculate the percentage of the initial Sr²⁺ concentration that precipitates as SrSO₄. (Assume no volume change.)
(d) Based on your calculations, evaluate whether adding this amount of sulfate ion accomplishes the stated goal of selectively precipitating Ba²⁺ with minimal loss of Sr²⁺. Support your conclusion with quantitative evidence.