Electrolytic Dissociation and Ionic Exchange Reactions
Mobile ions connect microscopic dissociation with electrical conductivity and the observable chemistry of aqueous solutions.
Learning goals
- Distinguish electrolytes from nonelectrolytes and strong from weak electrolytes.
- Write charge- and atom-balanced dissociation equations.
- Relate ion concentration to formula stoichiometry and degree of dissociation.
- Convert molecular equations into complete and net ionic equations.
- Recognize precipitation, neutralization, and gas-evolution drivers.
1. Ions and conductivity
An electrolyte produces mobile ions when dissolved in water or, for many ionic substances, when molten. Moving ions carry electric charge through the liquid. A nonelectrolyte may dissolve as neutral molecules and conduct poorly. Solid ionic crystals contain ions but normally do not conduct because those ions cannot move.
Water molecules surround dissolved ions in hydration shells. Dissociation separates pre-existing ions of an ionic solid, while ionization describes formation of ions from neutral molecular species; both can create conducting solutions.
2. Strong and weak electrolytes
| Type | Particle picture | Equation symbol |
|---|---|---|
| Strong electrolyte | nearly complete conversion to ions | single arrow, e.g. NaCl → Na+ + Cl− |
| Weak electrolyte | mostly molecules with a small ion fraction | equilibrium arrow, e.g. HA ⇌ H+ + A− |