Write a chemical equation for NH4 + (aq) showing how it is an acid or a base according to the Arrhenius definition. Express your answer as a chemical equation. Identify all of the phases in your answer.

NH4 + (aq) → NH3 (aq) + H + (aq)

Explanation:

Following arrhenius, an acid can be defined as:

An Arrhenius acid is a substance that, when added to water, increases the concentration of H + ions in water.

NH4 + (aq) → NH3 (aq) + H + (aq)

The ammonium ion acts as a weak acid in aqueous solution, dissociating into ammonia and a hydrogen ion.

An Arrhenius base is a substance that, when added to water, increases the concentration of OH - ions in water.

NH4 + (aq) will not dissciate in OH - ions. So it's not a base, but an acid.