conjugate acid-base pair

chemistry

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A conjugate acid-base pair consists of two chemical species that differ by a single proton (H⁺). According to the Brønsted-Lowry theory, an acid is a proton donor, and a base is a proton acceptor. When an acid loses a proton, it becomes its conjugate base, and when a base gains a proton, it becomes its conjugate acid.12

For example, in the reaction between hydrochloric acid (HCl) and ammonia (NH₃):
HCl (acid) + NH₃ (base) ⇌ Cl⁻ (conjugate base) + NH₄⁺ (conjugate acid)

Here, HCl and Cl⁻ form one conjugate pair, and NH₃ and NH₄⁺ form another. This concept is fundamental to understanding acid-base reactions, as it describes the transfer of protons between species.1324

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acid–base reaction
The Brønsted–Lowry definition
…and B together are a conjugate acid–base pair. In such a pair A must obviously have one more positive charge (or one less negative charge) than B, but there is no other restriction on the sign or magnitude of the charges.
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…and B together are a conjugate acid–base pair. In such a pair A must obviously have one more positive charge (or one less negative charge) than B, but there is no other restriction on the sign or magnitude of the charges.
Read More