conjugate+acids-bases

Conjugate Acids and Conjugate Bases
A //conjugate acid// is formed as the protonated product of an acid hydrolysis reaction.

It is the hydronium ion in traditional acid-water reactions:

HA (aq) + H 2 O (l) --> H 3 O + (aq) + A - (aq)

A //conjugate base// is the de-protonated form of the original acid (A -, above).

When a diprotic acid undergoes hydrolysis, it forms an amphoteric conjugate base:

In the case of sulfurous acid, the hydrogen sulfite ion (or bisulfite ion) is amphoteric:

H 2 SO 3 (aq) + H 2 O (l) --> H 3 O + (aq) + HSO 3 - (aq)

It can protonate another water molecule (i.e. act as an acid):

HSO 3 - (aq) + H 2 O (l) --> H 3 O + (aq) + SO 3 2- (aq)

It can also deprotonate a water molecule (i.e. act as a base):

HSO 3 - (aq) + H 2 O (l) --> OH - (aq) + H 2 SO 3 (aq)