Explain how to label a compound as a Bronstead-Lowry acid or base .

Explanation:

According to the Bronsted-Lowry conjugate acid-base theory:

1. An acid is a substance which looses donates protons and thus forming conjugate base.

2. A base is a substance which accepts protons and thus forming conjugate acid.

For example:

Here, is loosing a proton, thus it is considered as an acid and after losing a proton, it forms which is a conjugate base.

And, is gaining a proton, thus it is considered as a base and after gaining a proton, it forms which is a conjugate acid.