Question

Consider this two step mechanism for a reaction

Step 1     NO₂     +     Cl₂ ---------> ClNO₂     +     Cl slow; rate determining step

Step 2     NO₂     +     Cl ---------> ClNO₂ fast

a. What is the overall reaction?

b. Identify the intermediates in the mechanism.

c. What is the predicted rate law expression? Be sure to only list reactants from the overall equation and not intermediates in the rate law expression.

Answer 1

overall reaction can be obtained by adding both steps

the overall reaction is:

NO2 + Cl2 + NO2 + Cl —> ClNO2 + Cl + ClNO2

removing common species from both sides:

2 NO2 + Cl2 —> 2 ClNO2

2)

Cl is an intermediate because it is produced in step 1 and used up in step 2

3)

rate depends on slowest step

Here 1st step is slowest

So, rate law is:

rate = k[NO2][Cl2]