 In order to construct enough independent relationships to solve for all of the unknown rate constants, it is necessary to examine systems with different-excess.Consider again the simple example discussed above where the catalyst associates with substrate A, followed by reaction with B to form product P and free catalyst.Regardless of the approximation applied, multiple independent parameters ("k"2 and "K"1 in the case of pre-equilibrium; "k"1, "k"−1, and "k"2 in the case of steady-state) are required to define the system.