Strong electrolytes are completely dissociated into ions in water. The acid or base molecule does not exist in aqueous solution, only ions. Weak electrolytes are incompletely dissociated.
Strong acids completely dissociate in water, forming H+ and an anion. There are six strong acids. The others are considered to be weak acids. You should commit the strong acids to memory:
- HCl - hydrochloric acid
- HNO3 - nitric acid
- H2SO4 - sulfuric acid
- HBr - hydrobromic acid
- HI - hydroiodic acid
- HClO4 - perchloric acid
H2SO4 → H+ + HSO4-
A weak acid only partially dissociates in water to give H+ and the anion. Examples of weak acids include hydrofluoric acid, HF, and acetic acid, CH3COOH. Weak acids include:
- Molecules that contain an ionizable proton. A molecule wih a formula starting with H usually is an acid.
- Organic acids containing one or more carboxyl group, -COOH. The H is ionizable.
- Anions with an ionizable proton. (e.g., HSO4- → H+ + SO42-)
- transition metal cations
- heavy metal cations with high charge
- NH4+ dissociates into NH3 + H+
Strong bases dissociate 100% into the cation and OH- (hydroxide ion). The hydroxides of the Group I and Group II metals usually are considered to be strong bases.
- LiOH - lithium hydroxide
- NaOH - sodium hydroxide
- KOH - potassium hydroxide
- RbOH - rubidium hydroxide
- CsOH - cesium hydroxide
- *Ca(OH)2 - calcium hydroxide
- *Sr(OH)2 - strontium hydroxide
- *Ba(OH)2 - barium hydroxide
Examples of weak bases include ammonia, NH3, and diethylamine, (CH3CH2)2NH.
- Most weak bases are anions of weak acids.
- Weak bases do not furnish OH- ions by dissociation. Instead, they react with water to generate OH- ions.