Acid and Base Definitions

  • Acid: A proton () donor.
  • Base: A proton () acceptor.

Examiner's Tip

In exams, always use the word “proton” rather than “hydrogen ion”. It shows a higher level of theoretical understanding.

The Mechanism

Acids and bases do not exist in isolation. For something to act as an acid (donate ), something else must be there to act as a base (accept ).

Example 1: Dissolving Acid in Water

  • donates a proton to water.
  • accepts the proton (acting as a base).

Example 2: Reaction between Ammonia and HCl

  • donates a proton
  • accepts the proton using the one pair on the nitrogen atom.