Question

Which will happen when sodium sulfate is added to a saturated solution of $CaS{O}_4$ that is at equilibrium? $CaS{O}_4\left(s\right)\rightleftharpoons C{a}_2\left(aq\right)+S{O}_4^{2-}\left(aq\right)$

• A. The solubility of the calcium sulfate will decrease
• B. The concentration of calcium ikons will increase
• C. The reaction will shift to the right
• D. The $K_{sp}$ value will change
• E. The equilibrium will shift to consume the decrease in sulfate ions.

Answer 1

The correct option is A The solubility of the calcium sulfate will decrease

When sodium sulfate is added to a saturated solution of $CaS{O}_4$ that is at equilibrium, the solubility of the calcium sulfate will decrease due to common ion effect.
$CaS{O}_4\left(s\right)\rightleftharpoons C{a}_2\left(aq\right)+S{O}_4^{2-}\left(aq\right)$
$N{a}_{2}S{O}_4\to 2N{a}^{+}+S{O}_4^{2-}$
Sodium sulphate is a strong electrolyte and completely dissociates to give sulphate ions which act as common ions. The presence of sulphate ions depresses the ionisation of calcium sulphate.