What are conjugated acids and bases

to directory mode

Conjugated acid-base pairs

When an acid dissociates, we absorb a proton. so reacts as a base:

(Acid 1) + (Base 2) → +

The release of protons by an acid or the uptake of protons by a base is a reversible reaction. In the reverse reaction, the chloride ion reacts as a base and the hydronium ion as an acid:

(Acid 2) + (Base 1) → +

An equilibrium is established between the forward and reverse reactions. and are a conjugate acid-base pair, as well as and. The double arrows show that the forward and backward reactions take place simultaneously:

(Acid 1) + (Base 2)(Acid 2) + (Base 1)

: conjugate acid of the base: conjugate base of the acid

A conjugated acid-base pair differs by one proton.

The general notation of the dissociation equilibrium of an acid in aqueous solution looks like this:

Example for bases: In the case of ammonia, the back reaction turns the ammonium ion into an acid and the hydroxide ion into a base:

(Base 1) + (Acid 2)(Base 2) + (Acid 1)

: conjugate acid of the base: conjugate base of the acid

The general notation of the equilibrium reaction of a base in aqueous solution is:

The reaction equations show an interesting property of water: in the presence of hydrochloric acid, water reacts as a base, in the presence of ammonia it reacts as an acid. Depending on the conditions, water can either act as an acid or as a base. Substances with this property are called ampholytes.