APChemistryCollege BoardTopic QuestionsUnit 5: Kinetics5.8 Reaction Mechanism & Rate Law

Reaction Mechanism & Rate Law (College Board AP Chemistry)

Topic Questions

DownloadView
Medium
1a1 mark

Nitrogen dioxide, NO2(g) , is produced as a by-product of the combustion of fossil fuels in internal combustion engines. At elevated temperatures NO2(g) decomposes according to the equation below.

2 NO2(g)  →  2 NO(g) + O2(g)

The concentration of a sample of NO2(g) is monitored as it decomposes and is recorded on the graph directly below. The two graphs that follow it are derived from the original data.

q6-june-2019---ap-chemistry

Explain how the graphs indicate that the reaction is second order.

How did you do?

1b1 mark

Write the rate law for the decomposition of NO2(g) .

How did you do?

1c2 marks

Consider two possible mechanisms for the decomposition reaction.

 

i)
Is the rate law described by mechanism I shown below consistent with the rate law you wrote in part (b) ? Justify your answer.

 

Mechanism I

Step 1:

NO2(g) + NO2(g) → NO(g) + NO3(g)

slow

Step 2:

NO3(g) → NO(g) + O2(g)

fast

 

ii)
Is the rate law described by mechanism II shown below consistent with the rate law you wrote in part (b) ? Justify your answer.

 Mechanism II

Step 1:

NO2(g) + NO2(g)  rightwards arrow over leftwards arrow N2O4(g)

fast equilibrium

Step 2:

N2O4(g) → 2 NO(g) + O2(g)

slow

How did you do?

Did this page help you?