Chemical Concept Demonstrated

• Common-ion effect

Demonstration

AgNO3 and NaOAc are added to a beaker of water, and the solution is filtered. The crystallizing dishes are half-filled with the filtrate. AgNO3 is added to the first dish. NaOAc is added to the second.

Observations

AgOAc precipitates in both dishes.

Explanation (including important chemical equations)

The common-ion effect is the decrease in the solubility of a salt that occurs when the salt is dissolved in a solution that contains another source of one of its ions.  The filtrate is a saturated solution of Ag⁺ and OAc^- ions.  When either AgNO₃ or NaOAc is added to the filtrate, the solubility of the ions in the saturated solution decreases, and the Ag ⁺ and OAc^- ions crash out as AgOAc.

AgNO₃ (aq) + OAc ^- (aq) <=> AgOAc (s)

NaOAc (aq) + Ag ⁺ (aq) <=> AgOAc (s)

Contributors

• Dr. George Bodner (Perdue University)