IB Chemistry - Acids and Bases

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Acids are normally defined according to Arrhenius idea of an aqueous solution that contains free hydrogen ions. However, there are other theories which allow the definition of acids to be extended to cover other non-aqueous systems.

Syllabus reference

Reactivity 3.1.1 - Brønsted–Lowry acid is a proton donor and a Brønsted–Lowry base is a proton acceptor.

  • Deduce the Brønsted–Lowry acid and base in a reaction.


  • A proton in aqueous solution can be represented as both H+(aq) and H3O+(aq).
  • The distinction between the terms “base” and “alkali” should be understood.

Tools and links

  • Nature of science, Reactivity 3.4 - Why has the definition of acid evolved over time?

In Chapter 8.2