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
anor277
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-)]#.

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