What is a conjugate acid-base pair?

A conjugate acid-base pair consists of an acid and a base that differ by one proton. When an acid donates a proton, it forms its conjugate base, and when a base accepts a proton, it forms its conjugate acid.

For example, in the reaction between hydrochloric acid (HCl) and water (H2O): HCl + H2O -> H3O+ + Cl-

HCl donates a proton to water, forming the hydronium ion (H3O+) as its conjugate acid, and the chloride ion (Cl-) as its conjugate base.

Conjugate acid-base pairs are important in acid-base chemistry as they help maintain the equilibrium in a reaction. The strength of a conjugate acid-base pair is determined by the strength of the acid or base that formed it. Strong acids have weak conjugate bases, and strong bases have weak conjugate acids.