Finding the difference in solubility

Question

Consider the solubility of Ca(OH)2 in each of the following solutions. For each solution, indicate whether the Ca(OH)2 solubility will increase, decrease, or not change as compared to the solubility of Ca(OH)2 in water.

0.10 M RbOH

0.10 M KNO3

0.10 M HNO3

0.10 M CaBr2

Answer 1

Look for the common ion effect.

Ca(OH)₂(s) <==> Ca²⁺(aq) + 2OH^-(aq)

Ksp = [Ca²⁺][OH^-]²

Recall Le Chatelier's principle, addition of Ca²⁺ or OH^- will push rx toward left (insoluble)

Addition of acid (H⁺) will react with OH^- --> H₂O thus pulling rx to right (more soluble)

Ca(OH)₂ solubility in H₂O vs.....

RbOH - decrease in solubillity because of the common ion OH^-

KNO₃ - no change in solubility

HNO₃ - increase in solubility because OH^- essentially being removed

CaBr₂ - decrease in solubility because of common ion Ca²⁺