When a chemical reaction is at equilibrium, the concentration of each reactant and the concentration of each product must be
Answer and Explanation:
Most chemical reactions do not go to completion, but rather reach equilibrium. This is a state in which the rate of the forward reaction is equal to the rate of the reverse reaction. As reactants are making products, products are making reactants back at the same rate. If we were in a lab looking at the reaction at equilibrium, we would have a hard time noticing that it's at equilibrium since we would not see any noticeable changes. This is because the concentrations of reactants and products remain constant when a reaction has reached equilibrium. Therefore, choice 1 is the correct answer choice.