Chapter 17.3, Problem 29SSC

Interpretation Introduction

Interpretation:

The presence of a common ions reduces the solubility of an ionic compound is to be described.

Concept introduction:

According to Le Chatelier's principle, the solubility of a solute is decreases by adding common ions to the solution. It states that the reaction shifts towards the left side to relieve the stress of the excess product.

Answer to Problem 29SSC

By addition of the common ions to the solution, the solubility of the solute is decreases.

Explanation of Solution

Considered an example of a solution which is given as:

$\text{Ca}{\left({\text{PO}}_{\text{4}}\right)}_{\text{2 (S)}}\underset{}{\rightleftharpoons }{\text{3Ca}}^{\text{2+}}\left(\text{aq}\right){\text{ + 2PO}}_{\text{4}}{}^{\text{3-}}\left(\text{aq}\right)$

If $\text{CaCl2}$ is added to the $\text{Ca}{\left({\text{PO}}_{\text{4}}\right)}_{\text{2}}$ saturated solution, the ${\text{Ca}}^{\text{2+}}$ ion concentration will increases , making $\text{Qsp > Ksp}\text{.}$

So, by adding a common ion to the solution solubility of solute will decreases, as the reaction sifts toward the left to relieve the stress of the excess products according to Le Chatelier’s principle. In this way, the common ion effect usually decreases the solubility of a sparingly soluble salt.

Conclusion

By addition of the common ions to the solution, the solubility of the solute is decreases.