A more detailed analysis of Worked Problem

These two expressions for the steady state (Equation 8.148), and the equilibrium state (Equation 8.156), are kinetically distinct, and so the two mechanisms could be distinguished kinetically. However, there is a limiting case in which they cease to be distinguishable. 

Since K= ([R+]actual [X ]actual/[RX]actual)equil, if X [X ]actual then [R+]actual/ [RX]actual c 1. This implies that there is only a very small amount of R+ present, and that [RX]actual [RX]total. 

This is exactly the same expression as the approximate steady state expression, Equation (8.157), corresponding to the condition, k2[Y ] -C i [X ], which, in turn, corresponds to most of the R+ being removed by the back reaction, rather than by reaction with Y.  

Under these conditions the steady state and the pre-equilibrium state are indistinguishable. However, the conditions under which they become indistinguishable are different in each, i.e. 

Under these conditions, the steady state rate, Equation (8.158), and the preequilibrium rate are totally distinct and experiment should be able to distinguish 

---