Final answer:
The equilibrium constant for a reversed chemical reaction is the inverse of the original equilibrium constant. Changing the direction of a chemical equation reverses the roles of reactants and products, and so K' will equal 1/K of the forward reaction, where K' is the equilibrium constant of the reversed reaction.
Step-by-step explanation:
If a reaction is reversed in direction, the new value of the equilibrium constant (K') is the inverse of the original equilibrium constant (K). This means that whatever the numerical value of K was for the forward reaction, the equilibrium constant for the reversed reaction equals 1/K. The equilibrium constant is a reflection of the ratio of the concentrations of products to reactants at equilibrium; therefore, when the direction of a chemical equation is changed, the identities of 'reactants' and 'products' are switched. As a result, for a reversed reaction, if the original equation was aA + bB = cC + dD with an equilibrium constant K, the reverse reaction cC + dD = aA + bB would have an equilibrium constant K' = 1/K.
During the course of the reaction, as it moves toward equilibrium, the rates of the forward and reverse reactions change. They are initially at different rates but eventually adjust so that they become equal at equilibrium. However, the value of K or K' remains unchanged regardless of how reactants or products are varied or how the reaction is approached.