How can you identify an electrolyte from a compound's behavior?

• A. Does not conduct electricity in any state.
• B. Conducts electricity in aqueous solution or when melted; ionic compounds and strong acids/bases are electrolytes.
• C. Only melts conduct electricity but not in solution.
• D. Aqueous solutions always conduct electricity, regardless of solute.

Answer: (B)

Electrolytes are substances that form mobile ions in a medium, so they can carry an electric current. You can identify them by their conductivity: if a compound conducts electricity when dissolved in water or when melted, it is producing ions in that medium. Ionic compounds dissociate into ions in aqueous solution, and strong acids and bases also dissociate completely into ions, making the solution a good conductor. When an ionic compound is melted, the solid’s ions are free to move, so melting also allows conduction. In contrast, most covalent compounds that do not ionize—like sugar in water—don’t produce free ions and thus do not conduct electricity, so they’re non-electrolytes. There are also weak electrolytes that only partially ionize and conduct only weakly, but the guiding behavior is the presence of free ions in solution or melt.