Consider the reaction 2NO(g) + O2 ---> 2NO2 (g). The following mechanism has been proposed to explain the experimental rate law:
1. 2NO --> and <-- N2O2 (fast)
2. O2 + N2O2 --> 2NO2 (slow)
Give the rate law for the proposed mechanism. If necessary, use the pre-equilibrium assumption to determine an expression for the concentration(s) of any intermediate(s) that may appear in the derived rate law.© BrainMass Inc. brainmass.com October 24, 2018, 6:01 pm ad1c9bdddf
Since step 2 is the rate-determining step, the rate law is
rate = k2[N2O2][O2]...(1)
Now, we need to ...
This solution includes calculations for finding the required rate equation.
Rate Law mechanism observed
The rate law for the Br—- catalyzed reaction
C6H5NH2 + HNO2 + H+ C6H5N2+ + 2H2O
is observed to be rate = = k [H+][HNO2][Br -].
A proposed mechanism is
(1) H+ + HNO2 H2NO2+ (rapid equilibrium)
(2) H2NO2+ + Br- NOBr + H2O (slow)
(3) NOBr + C6H5NH2 C6H5N2+ + H2O + Br- (fast)
Deduce the rate law for this mechanism and relate the observed rate constant k to the rate constants appearing in the assumed mechanism.
1. Step (1) is a rapid equilibrium, meaning k1 and k-1 are much faster than k2.
2. The forward and reverse rates are equal for step (1) since it is an equilibrium; this fact can
be used to get an expression for the concentration of the intermediate H2NO2+.
3. Recall, the reaction orders for elementary reactions are determined by the reaction
4. Step (2) is sufficiently slow that it can be considered rate-determining.