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6.4: Electrolytes and Nonelectrolytes

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    538666

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    Learning Objectives
    • Define electrolytes and non electrolytes

    When some substances are dissolved in water, they undergo either a physical or a chemical change that yields ions in solution. These substances constitute an important class of compounds called electrolytes. Substances that do not yield ions when dissolved are called nonelectrolytes. If the physical or chemical process that generates the ions is essentially 100% efficient (all of the dissolved compound yields ions), then the substance is known as a strong electrolyte (good conductor). If only a relatively small fraction of the dissolved substance undergoes the ion-producing process, the substance is a weak electrolyte (does not conduct electricity as well).

    Substances may be identified as strong, weak, or nonelectrolytes by measuring the electrical conductance of an aqueous solution containing the substance. To conduct electricity, a substance must contain freely mobile, charged species. Most familiar is the conduction of electricity through metallic wires, in which case the mobile, charged entities are electrons. Solutions may also conduct electricity if they contain dissolved ions, with conductivity increasing as ion concentration increases. Applying a voltage to electrodes immersed in a solution permits assessment of the relative concentration of dissolved ions, either quantitatively, by measuring the electrical current flow, or qualitatively, by observing the brightness of a light bulb included in the circuit (Figure \(\PageIndex{1}\)).

    This diagram shows three separate beakers
    Figure \(\PageIndex{1}\): Solutions of nonelectrolytes, such as ethanol, do not contain dissolved ions and cannot conduct electricity. Solutions of electrolytes contain ions that permit the passage of electricity. The conductivity of an electrolyte solution is related to the strength of the electrolyte.

    Ionic Compounds - Strong Electrolytes

    When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround the ions. This process represents a physical change known as dissociation. Under most conditions, ionic compounds will dissociate nearly completely when dissolved, and so they are classified as strong electrolytes.

    The diagram shows eight purple spheres
    Figure \(\PageIndex{2}\): As potassium chloride (KCl) dissolves in water, the ions are hydrated. The polar water molecules are attracted by the charges on the K+ and Cl− ions. Water molecules in front of and behind the ions are not shown.

    Molecular Compounds - Non Electrolytes

    Molecular compounds are not composed of ions. If they are similar they will mix with water, but they will not dissociate. Therefore, they are considered non-electrolytes.

    Acids

    Acids are a very special category of molecular compound. Although they are molecular compounds, we have previously shown how they can create ions in aqueous solutions. That means they are electrolytes.

    Strong or Weak?

    Acids come in both the strong and weak electrolyte varieties. Most are weak, while just a few are considered strong. Although you may be provided a list by your instructor, a very simple way to check is a quick google search for "Which acids are strong?". Whatever is not on this list should be considered weak, meaning although it creates ions in solution, it does not ionize completely and create as many as a strong acid would.

    Example \(\PageIndex{1}\): Identifying Ionic Compounds

    Which compound(s) will dissolve in solution to separate into ions?

    Hint: First classify as ionic (metal + non-metal), molecular (all non-metals), or acid (formula starts with H)

    1. \(\ce{LiF}\)
    2. \(\ce{P_2F_5}\)
    3. \(\ce{C_2H_5OH}\)

    Solution

    \(\ce{LiF}\) will separate into ions when dissolved in solution, because it is an ionic compound. \(\ce{P_2F_5}\) and \(\ce{C_2H_5OH}\) are both covalent and will stay as molecules in a solution.

    Exercise \(\PageIndex{1}\)

    Which compounds will dissolve in solution to separate into ions?

    1. C6H12O11, glucose
    2. CCl4
    3. CaCl2
    4. AgNO3
    Answer
    c & d

    Contributions & Attributions

    This page was constructed from content via the following contributor(s) and edited (topically or extensively) by the LibreTexts development team to meet platform style, presentation, and quality:

    This page titled 6.4: Electrolytes and Nonelectrolytes was last modified on Tue, 16 Dec 2025 03:18:15 GMT and is shared under a mixed license and was authored, remixed, and/or curated by Seth Yates.