Weak Acid
An acid that ionises only partially in aqueous solution, establishing an equilibrium with its conjugate base.
Formula / equation
HA ⇌ H⁺ + A⁻
Unit
mol/L
In depth
Only a small fraction of molecules donate their proton, so the solution contains mostly undissociated acid and the pH is much higher than for a strong acid of the same concentration. The extent of ionisation is quantified by Ka and increases on dilution.
Examples in the real world
Ethanoic acid, carbonic acid, hydrofluoric acid and the carboxylic acids generally.