Question

What exactly makes the product or the reactant concertation larger than the other when the reaction producing the products (forward reaction) and the reaction producing the reactants (reverse reaction) have the same rate, and rate is change in concentration over time. If the rates of the reactions are the same, (and obviously the initial concentrations of the reaction species have no effect on K), then there must be another factor affecting the concentrations of the reactants at equilibrium, but what is it?

Answer 1

At chemical equilibrium, rates of the forward and reverse reactions are the same and concentrations remain constant. Factors like changes in concentration can shift the reaction to re-establish equilibrium, consistent with the equilibrium constant. Equilibrium concentrations depend on the dynamic balance between the forward and reverse reactions.

Step-by-step explanation:

Factors Affecting Equilibrium Concentrations

When a chemical reaction reaches equilibrium, the rates of the forward and reverse reactions are the same, and the concentrations of reactants and products remain constant. However, several factors can affect the relative concentrations of reactants and products at equilibrium. Factors such as the change in concentration of either reactants or products can shift the reaction in favor of the forward or the reverse direction. This explains the Le Châtelier's Principle, which states that the system will adjust to minimize the change. In the context of the reaction quotient (Qc), as the reaction proceeds toward equilibrium in the forward direction, the concentration of reactants decreases, product concentration increases, and Qc increases until it is equal to the equilibrium constant (Kc). If Qc is different from Kc, the system is not at equilibrium and will shift to reach it.

Changes in concentration cause the reaction to undergo a temporary shift to re-establish equilibrium. For example, if the concentration of a reactant is decreased, the rate of the forward reaction will slow down, and the reverse reaction will be favored until the equilibrium is re-established with possibly different concentrations of reactants and products consistent with the value of Kc. Similarly, increasing the concentration of a product will favor the reverse reaction, leading to the formation of more reactants.

Overall, at equilibrium, the ratio of the concentrations of products to reactants, defined by the equilibrium constant (Kc), remains constant. The actual concentrations of products and reactants depend on the specific reaction being considered and are governed by the dynamic balance between the forward and reverse reactions.