Question

Consider this overall reaction, which is experimentally observed to be second order in AB and zero order in C.

AB + C ---> A + BC

Is the following mechanism valid for this reaction? Why or why not?

AB + AB ----> AB₂ + A (slow)

AB₂ + C ----> AB + BC (fast)

Answer 1

Consider this overall reaction, which is experimentally observed to be second order in AB and zero order in C.

AB + C ---> A + BC

the following mechanism is valid for this reaction

AB + AB ----> AB₂ + A (slow)

AB₂ + C ----> AB + BC (fast)

because

we know that the rate determining step is the slowest step in the mechanism.

therefore

for the reaction step

AB + AB ----> AB₂ + A (slow)

we have

rate = k [AB]^2

and this the rate of the slowest step and therefore rate of the reaction is

rate = k [AB]^2

therefore

we can say that the given mechanism is valid because the mecahnism shows that the reaction is second order in AB and zero order in C.