Rate and Equilibrium confusion

[Yearningformedschool!]

Hi all! I was hoping someone can clear my confusion regarding rate and equilibrium. The Keq of the hypothetical reaction is equal to the Kf/Kr. So in the following reaction: aA+bB <--> cC+dD, the Keq is equal to [C]^c+ [D]^d/ [A]^a+^^b. My point of confusion is the powers in which the concentrations are raised. Aren't these powers, or superscripts, determined experimentally, to show the order of the reaction? So how can the concentrations just be raised to those powers? Thanks!

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[aldol16]

Keq = kf/kr only applies for elementary steps. This is implied since "forward" and "reverse" implies a single, reversible step. It's meaningless to give a "kf" for a series of two or three steps because you get an apparent rate constant and not the actual kf1, kf2, kf3, etc. Since this equation only applies for elementary steps, the reaction coefficients can be used since the powers in the rate equations for elementary steps are the reaction coefficients.