What happens when a fast reversible step(s) occurs prior to the
rate-determining step?
2NO(g) + O2(g) 2NO2 (g)
Rate law: rate = k[NO]2[O2]
Step 1: NO(g) + O2(g) NO3(g) fast and reversible
Step 2: NO3(g) + NO(g) 2NO2(g) slow; rate-determining
Proposed Mechanism
Rate laws for the two elementary steps:
Step 1: rate1 (fwd) = k1[NO][O2]; rate1 (rev) = k-1[NO3]
Step 2: rate2 = k2[NO3][NO]
Step 2 (rate-determining) contains [NO3] which does
not appear in the experimental rate law!
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