Acid-Base Hydrolysis

A hydrolysis reaction is one that involves water. Acids and bases that are aqueous in nature will undergo reactions with water.

Here is the general equation for an acid hydrolysis reaction, where A = any anion:

HA (aq) + H2O (l) --> H3O+ (aq) + A- (aq)

The bold section of the reaction is the most important part - water is acting as a base (proton acceptor), and forming the hydronium ion (H3O+), which is going to be the common denominator in all acid hydrolysis reactions. The anion loses an oxidation state (it lost a positively charged proton).

Here is one example, using nitric acid:

HNO3 (aq) + H2O (l) --> H3O+ (aq) + NO3- (aq)

Watch an animation of acid dissociation here.

A base hydrolysis reaction follows the chemical equation below (where B is any base):

B (aq) + H2O (l) --> OH- (aq) + HB+ (aq)

Again, the bold section of the above equation is the common factor in all base hydrolysis reactions. Water is now acting as an acid (donating a proton), and will form the hydroxide ion (OH-). The base will gain an oxidation state with the addition of the positively charged proton.

Look at the following example involving the sulfate ion:

SO42- (aq) + H2O (l) --> OH- (aq) + HSO4- (aq)

Try some example problems on this worksheet: