Skip to main content
Library homepage
Chemistry LibreTexts

The Common-Ion Effect

  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    Chemical Concept Demonstrated

    • Common-ion effect


    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.


    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)


    The Common-Ion Effect is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

    • Was this article helpful?