Irreversible Reactions

Chemical reactions that proceed in one direction only, that is, from the reactant side to the product side only, are called irreversible reactions. Will go to completion.

Two types of reactions that are irreversible: Neutralization & Combustion.

Reversible Reactions

On the contrary, many chemical reactions do not go to completion. The reaction may proceed from left to right (from reactant to product), this is called forward reaction; and the reaction may reverse from right to left (from product to reactant), this is called backward reaction. Reversible reactions proceed in both directions.