What condition must occur when a chemical reaction is at equilibrium?

Concentration = Constant

Explanation:

The conditions that must occur when a chemical reaction is at equilibrium are as follows -

At equilibrium there is no net change in the amounts of reacting species and product forming species and the concentration of the reactants and products are constant.

A reaction is is said to be in chemical equilibrium if the rate of the forward reaction and the rate of the backward reaction is equal.