11.2 Electrolytes - Chemistry 2e | OpenStax

Learning Objectives

Define and give examples of electrolytes.
Distinguish between the physical and chemical changes in ionic and covalent electrolytes.
Relate electrolyte strength to solute-solvent attractive forces.

Substances that yield ions in solution when dissolved in water are called electrolytes.
Nonelectrolytes: Substances that do not yield ions.
Strong Electrolytes: Substances where the ion-producing process is nearly 100% efficient.
Weak Electrolytes: Substances where only a small fraction undergoes the ion-producing process.

Electrical conductance is a measure to identify strong, weak, or nonelectrolytes.
Conducting electricity requires freely mobile, charged species (e.g., electrons in metals or ions in solutions).
Conductivity increases with ion concentration.
Voltage applied to electrodes can assess ion concentration either quantitatively or qualitatively.
Solutions of nonelectrolytes, like ethanol, do not conduct electricity as they lack dissolved ions.

Water and polar molecules are attracted to ions via ion-dipole attractions, assisting in ionic compound dissolution.
Dissolution process:
- Ionic compounds separate into ions in solution due to solvation by water.
- This physical change is called dissociation.
- Ionic compounds that dissociate completely are strong electrolytes.
Example: Dissolution of KCl in water, where water solvates K+ and Cl- ions, allowing them to move freely.

Pure water is a poor conductor due to low ionization.
Ionization of water:
- Water molecules can ionize to form hydronium (H3O+) and hydroxide (OH-) ions.
Some covalent compounds conduct electricity when they react with water to produce ions.
Example: HCl gas in water ionizes completely, making it a strong electrolyte.
Strong acids like HCl are strong electrolytes due to complete ionization.
Weak acids and bases partially ionize, resulting in weak electrolyte behavior.
Reaction example: HCl + H2O → H3O+ + Cl- (essentially 100% ionization).