Which of the following can function as both a Bronsted Lowry acid and base in water?

Question

1. HCl

2. HPO4 (2-)

3. NH2 (-)

4. H30 (+)

5. NaOH

What are the products when NaOH dissociates in water? Is it a Bronsted Lowry acid or base... it doesn't accept H or donate H

Answer 1

A Bronsted Lowry acid is any substance that can donate a hydrogen ion. A Bronsted Lowry base is any substance that can receive a hydrogen ion. That means a substance that is both can both donate and receive a hydrogen ion and form a substance.

The answer is HPO4 (2-), because when it donates a hydrogen ion, it is an acid, and forms PO4 (3-). When it receives a hydrogen ion, it becomes H2PO4(-).

All the other choices cannot possibly form other substances when adding AND substracting hydrogen ions.