A strong acid is an acidic compound which ionizes completely or almost completely in aqueous solution.
pH is the measure of acidity/base strength. It is defined well for aqueous solutions as the -log10(M[H+]) - the negative of the log (base 10) of the concentration of Hydrogen (or more accurately hydronium, H3O+) ions in soultion. Neutral pure water at STP has an equilibrium concentration of 1 hydronium ion per 10,000,000 water molecules (M = 10 ^-7 ) and thus has a pH of 7.
Acidic materials have a pH lower than this and bases have a pH higher than this.
The corresponing basic equivalents are the strong bases.
Examples of strong acids:
- Hydrochloric acid
- Nitric acid
- Sulphuric acid
- Hydrobromic acid
- Hydroiodic acid
- Trichloro acetic acid
- Perchloric acid
(The analogical way to differentiate between strength of the strong bases is to use liquid ammonia as a diluent, instead of water).
- See also: Weak acid