What is true when a reaction has reached equilibrium?

the concentration of products and reactants is constant.

the reaction has stopped.

the concentration of the products is changing.

the concentration of the reactants is changing.

The concentration of the products and reactants is constant.

Explanation:

Once the reversible reaction that proceeds forward and backward simultaneously has reached it's state of chemical equlibrium, the concentration of products and reactants become constant.

This means that the rate at which the reactants react to form products becomes equal to the rate at which products react to form the reactants again. At this point there will be no further change in the concentration of reactants and products with time. In chemical equilibrium the concentration of a reactant or a product is expressed in moles per cubic decimeter ( mol / dm^3.