Define a conjugate pair according to the Brønsted-Lowry theory. - Leaving Cert Chemistry - Question e - 2009

In the Brønsted-Lowry theory, a conjugate pair consists of two species that differ by the presence of a proton (H⁺).

1. Acid and Conjugate Base: An acid is a substance that donates a proton (H⁺) to form its conjugate base. This process can be represented as:

   [ HA \rightleftharpoons A^- + H^+ ]

   where (HA) is the acid and (A^-) is its conjugate base.

2. Base and Conjugate Acid: A base is a substance that accepts a proton (H⁺) to form its conjugate acid. This can be symbolized as:

   [ B + H^+ \rightleftharpoons BH^+ ]

   where (B) is the base and (BH^+) is its conjugate acid.

In summary, the conjugate pair is formed when an acid and its conjugate base or a base and its conjugate acid are related through the transfer of protons.