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# Reaction Mechanism Based on Rate Expression

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Problem:
For the reaction: 2H2(g)+2NO(g)--> N2(g)+2H2O(g)
The observed rate expression is: rate=k[NO]^2[H2]

Which of the following mechanisms is/are consistent with the overall reaction and the rate expression?
a. Single step 2H2 + 2NO --> N2 + 2H2O
b. Step 1 H2 + NO --> H2O + N (slow)
Step 2 N + NO --> N2 + O
Step 3 O + H2 --> H2O

c. Step 1 H2 + 2NO --> N2O + H2O (slow)
Step 2 H2 + N2O --> N2 + H2O

d. Step 1 2 NO (equilibrium arrows)N2O2
Step 2 N2O2 + H2 --> N2O + H2O (slow)
Step 3 N2O + H2 --> N2 + H2O

e. more than one of these mechanism (a-d) is consistent

E is the answer to this question, but could you please include an explanation of the process, as well.

https://brainmass.com/chemistry/chemical-kinetics/reaction-mechanism-based-rate-expression-242718

#### Solution Preview

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The rate law is always dependent on the slowest step.

a. Single step: 2H2 + 2NO --> N2 + 2H2O

There is only one step, so it must be the slowest. On the reactant side, 2 H2 are used and 2 NO are used. This would suggest the rate law is R = k[H2]2[NO] 2. This ...

#### Solution Summary

This solution explains how to determine a reaction mechanism based on an overall rate expression of a reaction.

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