Steady-state Approximation and Rate-determining Step: Example Problems
Try to solve these problems before watching the solutions in the screencasts.
Example Problem 1
Compare the rate expression obtained by applying the steady-state approximation to a sequence of elementary steps to the measured rate expression.
Overall reaction: \(2A \, + \, B\, \rightleftarrows \, A_2B\)
Experimental rate expression: \(r_{_{A_2B}}\, = \,[0.72(A)^2(B)]/[1\,+\,2(A)]\)
Elementary steps:
\(A \,+\, B \, \overset{k_1}{\underset{k_{-1}}\rightleftarrows} \, AB^*\)
\(AB^* \,+\, A \, \overset{k_2}{\underset{k_{-2}}\rightleftarrows} \, A_2B\)
Example Problem 2
Derive the rate expression for the Eley-Rideal surface reaction represented by the following mechanisms:
\(A(g) \,+\, S\, \rightleftarrows \, A \cdot S\)
\(A \cdot S \,+\, B(g) \, \rightleftarrows \, AB \cdot S\)
\(AB \cdot S \, \rightarrow \, AB(g)\)
where \(S\) represents an adsorption site on the catalyst surface