4.1 Solutions and Electrolytes

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    What is a Solution?

    A solution is composed of a solvent and one or more solutes.


    The solvent is a liquid and is present in a higher concentration than any of the solutes.


    The solute is dissolved in the solvent. It can be a solid, liquid, or gas.

    What are Electrolytes?

    Electrolytes dissolve in water to form ions making the solution electrically conductive.  They include ionic compounds, acids, and bases.


    Strong electrolytes dissociate into ions completely.


    Weak electrolytes dissociate into ions only partially.


    Nonelectrolytes can dissolve in water but don’t form ions.

    How to Identify Electrolytes?

    Strong Electrolytes

    1. Soluble Ionic Compounds

    2. Strong Acids ((HCl, HBr, HI, HClO4 HClO3, H2SO4, HNO3)

    3. Strong Bases (Group I metal hydroxides, Ba(OH)2, Sr(OH)2, Ca(OH)2)


    Weak Electrolytes

    1. Weak Acids (ex. HF, HCN, CH3COOH, etc.)

    2. Weak Bases (ex. NH3, CH3NH2, etc.)



    Molecular compounds (except acids/bases) (ex. C6H12O6 and CH3OH)

    Solubility Rules for Ionic Compounds

    Soluble Ionic Compounds
    Compounds containing
    NO3- and CH3COO- (acetate) None
    Cl-, Br-, I- Ag+, Hg22+, Pb2+
    SO42- Sr2+, Ba2+, Hg22+, Pb2+
    Insoluble Ionic Compounds
    Compounds containing
    S2- NH4+, Li+, Na+, K+, Rb+, Cs+, Ca2+, Sr2+, Ba2+
    CO32- NH4+, Li+, Na+, K+, Rb+, Cs+
    PO43- NH4+, Li+, Na+, K+, Rb+, Cs+
    OH- NH4+, Li+, Na+, K+, Rb+, Cs+, Ca2+, Sr2+, Ba2+