Acids and Bases
Defining Acids and Bases
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The Arrhenius Theory
Acids ionise in aqueous solutions to produce H+ ions
Hydrogen ions (H+) will combine with water (H2O) to form hydronium (H3O+) this is because free protons are unstable in water, so they quickly combine with water particles to for hydronium ions.
Bases dissociate in aqueous solutions to produce OH- ions
Neutralisation occurs when H+ reacts with OH- to form H2O
The Arrhenious Theory is limited because it only applies to interactions in aqueous solutions (acids and bases dissolved in water)
The Brønsted-Lowry Theory
Acids are "proton donors" (they donate H+ ions)
Bases are "proton acceptors" (they accept H+ ions)
Both acids and bases exist in conjugate pairs
Once an acid has donated a proton (H+ ion), it has the potential to accept a proton (effectively acting as a base). This is a conjugate base.
The same applies to bases (when a base accepts a proton, it becomes a conjugate acid with the potential to act as an acid by donating a proton)
“Conjugate Pairs” are 2 chemical species that differ only by a H+ ion
Davy's Theory
Davy’s Acids are substances which contain a H+ ion that can be replaced by a reactive metal
Davy’s Bases are substances which react with acids to form a salt and water
Properties of Acids and Bases
