To classify a substance as an Arrhenius acid or base, or as a Brønsted-Lowry acid or base, you must consider how the substance behaves when it dissolves in water. Ammonia forms an aqueous solution according to the following chemical equation.

NH3 (aq) + H2O (l) ⇌NH4 + (aq) + OH - (aq)

Based on this equation, which statement is correct?

a

Ammonia is an Arrhenius base but not a Brønsted-Lowry base.

b

Ammonia is a Brønsted-Lowry base but not an Arrhenius base.

c

Ammonia is an Arrhenius base and a Brønsted-Lowry base.

d

Ammonia is neither a Brønsted-Lowry base nor an Arrhenius base.

Ammonia is an Arrhenius base and a Brønsted-Lowry base.

Explanation:

An Arrhenius base is any substance which, when it is dissolved in an aqueous solution, produces hydroxide (OH^-), ions in solution. An aqueous solution is a solution that has water present in it.

A Bronsted-Lowry base is a substance that accepts a proton, that is, a hydrogen ion (H^+).

Looking at the equation above, ammonia satisfies both characteristics. We can see that when ammonia is dissolved in water, hydroxide ions is produced in the solution. Hence it is an Arrhenius base. Similarly, the hydroxide ion is formed when ammonia accepts a proton. This is a characteristic of a Brownstead-Lowry base. Hence ammonia is both an Arrhenius base and a Brownstead-Lowry base.