25.1.1—Terms: conjugate acid and conjugate base

In Brønsted–Lowry chemistry, an acid donates a proton and a base accepts one. The conjugate acid of a base is the species after it gains H+, while the conjugate base of an acid is what remains after it loses H+.

Conjugate pairs differ by exactly one proton. Water can act as either acid or base, so identify the direction from the equation.

NH₃/NH₄⁺ is a base/conjugate-acid pair; H₂O/OH⁻ is an acid/conjugate-base pair.

Conjugate does not mean “opposite charge” alone; track the proton transfer.