After 20.0g of Na_2SO_4 are added to a 0.5 L saturated solution of CaSO_4, does the concentration of Ca^(2+) increase, decrease, or stay the same?

1 Answer
Apr 1, 2016

[Ca^(2+)] will reduce.

Explanation:

The calcium sulfate is saturated. That is, the reaction,

Ca^(2+) + SO_4^(2-) rightleftharpoons CaSO_4(s) is at equilibrium. The addition of more sulfate anion will drive the equilibrium to the right. Calcium sulfate will precipitate, with reduction in [Ca^(2+)], so that the ion product resatisfies the solubility expression, K_(sp) = [Ca^(2+)][SO_4^(2-)].