Hydrolysis constant

A hydrolysis constant is an equilibrium constant for a hydrolysis reaction.[1]

For example, if a metal salt such as AlCl3 dissolves in an aqueous solution, the metal cation behaves as a Lewis acid and hydrolyzes the water molecules in the solvent.[2]

Al3+ + 2H2O AlOH2+ + H3O+

The hydrolysis constant for this reaction is as shown:

Khydrolysis = [H3O+] * [AlOH2+] / [Al3+]

In a more generalized form, the hydrolysis constant can be described as:

Ka = [H3O+] * [A] / [HA]

where A represents any base, and HA represents any acid.[3]


  1. Definition of hydrolysis_constant - Chemistry Dictionary
  2. Research and Education Association. The best test preparation for the GRE Chemistry test., 2000. ISBN 0-87891-600-8. Page 87.
  3. Hydrolysis

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