IB Chemistry SL

Revision Notes

8.1.2 Conjugate Acid-Base Pairs

Conjugate acid-base pairs

  • A Brønsted acid is a species that can donate a proton
  • A Brønsted base is a species that can accept a proton
  • In a reaction equilibrium the products are formed at the same rate as the reactants are used

Conjugate Acids & Bases equation

  • The reactant CH3COOH is linked to the product CH3COOby the transfer of a proton from the acid to the base
  • Similarly, the H2O molecule is linked to H3O+ ion by the transfer of a proton
  • These pairs are therefore called conjugate acid-base pairs
  • A conjugate acid-base pair is two species that are different from each other by a H+ ion
    • Conjugate here means related
    • In other words, the acid and base are related to each other by one proton difference

Amphiprotic species

  • Species that can act both as acids and bases are called amphiprotic
    • Eg. water as a Brønsted-Lowry acid

Equilibria Water as Brønsted -Lowry Acid, downloadable AS & A Level Chemistry revision notes

The diagram shows water acting as a Brønsted-Lowry acid by donating a proton to ammonia which accepts the proton using its lone pair of electrons

Equilibria Dot & Cross Diagram of Reaction between Water and Ammonia, downloadable AS & A Level Chemistry revision notes

The diagram shows a dot & cross diagram for the reaction of water with ammonia to show how water acts as a Brønsted-Lowry acid and ammonia as a Brønsted-Lowry base

  • Eg. water as a Brønsted-Lowry base

Equilibria Water as Brønsted -Lowry Base, downloadable AS & A Level Chemistry revision notes

The diagram shows water acting as a Brønsted-Lowry base by accepting a proton from hydrochloric acid proton using its lone pair of electrons

Equilibria Dot & Cross Diagram of Reaction between Water and Hydrochloric Acid, downloadable AS & A Level Chemistry revision notes

The diagram shows a dot & cross diagram for the reaction of water with hydrochloric acid to show how water acts as a Brønsted-Lowry base and ammonia as a Brønsted-Lowry acid

Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top