The Bronsted-Lowry theory states that an acid is a substance which donates protons, and a base is a substance that accepts protons.

The equilibrium law can be applied to aqueous solutions of acids.

For example, the following equilibrium is established in an aqueous. solution of ethanoic acid:

CH₃COOH_(aq) + H₂0_(l) CH₃COO^-_(aq) + H₃0⁺_(aq)

The equilibrium constant is given by:

Or

Ka is the Acid dissociation constant which is a measure of the strength of an acid.

pKa = lgKa - for most acids this gives the range of values between 0-14. Strong acids have low pKa values.

Kw is the ionic product of water, it is based on the equilibrium that occurs due to waters ability to self-ionise.

Kw = [H+][OH-]

At 25°C it has a value of 1.0 x 10^-14

pKw = 14.

To calculate pH:

pH = -lg [H+]

A buffer is a solution in which the pH of which does not change significantly when small amounts of acid or base is added to it.

Solubility product is a measure of a compounds solubility: Ksp.