The distribution of reactants and products in a chemical reaction mixture at equilibrium is not determined by a fixed ratio, such as 50% reactants and 50% products. Instead, it is determined by the specific equilibrium constant (K) for the reaction.
The equilibrium constant (K) expresses the ratio of the concentrations (or partial pressures) of products to reactants at equilibrium, with each species raised to the power of their respective stoichiometric coefficients. The expression for the equilibrium constant depends on the balanced chemical equation for the reaction.
For a general reaction:
aA + bB ⇌ cC + dD
The equilibrium constant expression (K) is:
K = ([C]^c [D]^d) / ([A]^a [B]^b)
The value of K remains constant at a given temperature for a specific reaction. However, the actual concentrations of reactants and products at equilibrium depend on the initial concentrations and the stoichiometry of the reaction.
If the equilibrium constant (K) for a reaction is large (K >> 1), it suggests that the equilibrium mixture will have a higher concentration of products compared to reactants. Conversely, if the equilibrium constant (K) is small (K << 1), the equilibrium mixture will have a higher concentration of reactants.</p>
Therefore, the actual distribution of reactants and products at equilibrium depends on the relative magnitudes of the forward and reverse rate constants and is determined by the specific equilibrium constant (K) for the reaction. It does not necessarily correspond to an equal concentration of reactants and products, such as 50% each.