Skip to main content
Chemistry LibreTexts

4.5: Solubility of Ionic Compounds

  • Page ID
    366259
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

    ( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\id}{\mathrm{id}}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\kernel}{\mathrm{null}\,}\)

    \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\)

    \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\)

    \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    \( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

    \( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

    \( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vectorC}[1]{\textbf{#1}} \)

    \( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

    \( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

    \( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    Learning Objectives
    • Predict solubilities of ionic compounds in water using the solubility rules.

    The extent to which a substance may be dissolved in water, or any solvent, is quantitatively expressed as its solubility, defined as the maximum concentration of a substance that can be achieved under specified conditions. Substances with relatively large solubilities are said to be soluble. A substance will precipitate when solution conditions are such that its concentration exceeds its solubility. Substances with relatively low solubilities are said to be insoluble, and these are the substances that readily precipitate from solution. More information on these important concepts is provided in the text chapter on solutions. For purposes of predicting the identities of solids formed by precipitation reactions, one may simply refer to patterns of solubility that have been observed for many ionic compounds (Table \(\PageIndex{1}\)).

    Table \(\PageIndex{1}\): Solubilities of Common Ionic Compounds in Water
    Soluble compounds contain Exceptions to these solubility rules include
    • group 1 metal cations (Li+, Na+, K+, Rb+, and Cs+) and ammonium ion \(\left(\ce{NH4+}\right)\)
    • the halide ions (Cl, Br, and I)
    • the acetate \(\ce{(C2H3O2- )}\), bicarbonate \(\ce{(HCO3- )}\), nitrate \(\ce{(NO3- )}\), and chlorate \(\ce{(ClO3- )}\) ions
    • the sulfate \(\ce{(SO4- )}\) ion
    • halides of Ag+, \(\ce{Hg2^2+}\), and Pb2+
    • sulfates of Ag+, Ba2+, Ca2+, \(\ce{Hg2^2+}\), Pb2+, and Sr2+
    Insoluble compounds contain Exceptions to these insolubility rules include
    • carbonate \(\ce{(CO3^2- )}\), chromate \(\ce{(CrO4^2- )}\), phosphate \(\ce{(PO4^3- )}\), and sulfide (S2−) ions
    • hydroxide ion (OH)
    • compounds of these anions with group 1 metal cations and ammonium ion
    • hydroxides of group 1 metal cations and Ba2+
    Example \(\PageIndex{1}\): Predicting Precipitation Reactions

    Use table \(\PageIndex{1}\) to predict the solubility of each of the following ionic compounds.

    1. barium sulfate
    2. silver chloride
    3. lead(II) nitrate

    Solution

    (a) According to the solubility table the presence of SO42- renders the compound soluble except when SO42- is combined with Ag+, Ba2+, Ca2+, \(\ce{Hg2^2+}\), Pb2+, and Sr2+. Since BaSO4 has Ba2+, it is insoluble.

    (b) According to the solubility table the presence of Cl- renders the compound soluble except when Cl- is combined Ag+, \(\ce{Hg2^2+}\), and Pb2+. Since AgCl has Ag+, it is insoluble.

    (c) According to the solubility table the presence of NO3- renders the compund soluble with no exception. Therefore, Pb(NO3)2 is soluble.

    Exercise \(\PageIndex{1}\)

    Use table \(\PageIndex{1}\) to predict the solubility of each of the following ionic compounds.

    1. calcium hydroxide
    2. ammonium carbonate
    3. mercury(I) bromide
    Answer

    (a) insoluble; (b) soluble; (c) insoluble

    Predicting the Solubility of Ionic Compounds: https://youtu.be/U3QNwnfmvGU

    Summary

    Solubility is the maximum amount of solute that can dissolve in specific amount of solvent. Not all ionic compounds are able soluble in water. We use the solubility rules to predict whether an ionic compound dissolves in water or not.

    Glossary

    Solubility

    Solubility is the maximum amount of solute that can dissolve in specific amount of solvent


    4.5: Solubility of Ionic Compounds is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

    • Was this article helpful?