Conjugate Acid vs Conjugate Base: The Difference
You write out a reaction, the mark scheme says "identify the conjugate base", and suddenly every species on the page looks like a candidate. The good news is that the answer is never a judgement call. There is a mechanical test, and it takes about three seconds. The short answer: a conjugate base is what is left of an acid after it donates a proton (H⁺); a conjugate acid is what a base becomes after it accepts one. The two members of a conjugate pair always differ by exactly one H⁺ — one hydrogen and one unit of charge — and nothing else. Quick comparison at a glance Feature Conjugate acid Conjugate base Formed by A base gaining H⁺ An acid losing H⁺ Change in formula One H added One H removed Change in charge More positive by 1 More negative by 1 Where to find it Opposite the base it came from Opposite the acid it came from Example NH₃ → NH₄⁺ CH₃COOH → CH₃COO⁻ Its own role Can donate that H⁺ back Can accept an H⁺ back What ...