Question

The reaction of NO and O2 produces NO2.
2 NO(g) + O2(g) „_ 2 NO2(g)
The reaction is second-order with respect to NO(g) and first-order with respect to O2(g). At a given temperature, the rate constant, k, equals 4.7 x 10^2 M^¡V2s^¡V1. What is the rate of reaction when the initial concentrations of NO and O2 are 0.025 M and 0.015 M, respectively?

Show your work: I thought it was
1/0.025-1/0.015=4.7 x 10^2 M^¡V2s^¡V1

but that is not right b/c the answer is 4.4 x 10^-3 M/s

Answer 1

You're trying to solve the problem wrong. Since one is first order and the other is second order, that equation won't work; besides, you have only one concn. What you want to use is the rate equation of
rate = k(NO)^2(O2)
Plug in k, NO, and O2 and calculate rate. 4.4E-3 is the right answer.

Answer 2

The rate constant for a first-order reaction is 1.6 × 10–2 s–1 at 664 K and 3.9 × 10–2 s–1 at 866 K. What is the activation energy? (R = 8.314 J/K⋅mol)