Question

How to know when something an acid or base

Answer 1

There are two types of acid/bases: 1) Brønsted acid/bases; 2) Lewis acid/bases.

1) Brønsted definitions of acids and bases:

• An acid is a species having a tendency to lose a proton

• A base is a species having a tendency to accept a proton

Example: CH₃COOH + NH₃ $\leftrightarrow$ NH₄⁺ + CH₃COO^–

Here CH₃COOH is an acid, NH₃ is a base; and NH₄⁺ is an acid, CH₃COO^- is a base.

2) Lewis definitions of acids and bases:

• Acids are electron pair acceptors.

• Bases are electron pair donors.

T.W.G. Solomons, C.G. Fryhle, Organic Chemistry, John Wiley & Sons, INC., 2011