Download AP Chemistry Kinetics WS 2 (Chapter 16) Integrated Rate Laws

AP Chemistry Kinetics WS 2 (Chapter 16)
Integrated Rate Laws
1. Draw and label the graphs that represent a zero-order, first-order, and second-order reaction.
2. The decomposition of NH3 gas on tungsten metal follows zero-order kinetics with a rate constant of 3.4 x
10-6 mol L-1s-1. If the initial concentration of NH3(g) is 0.0068 M, what will be the concentration after
1000s?
3. The decomposition of hydrogen peroxide is first-order in H2O2.
a. How long will it take for half of the H2O2 in a 10-gallon sample to be consumed if the rate
constant for the reaction is 5.6 x 10-2 s-1.
b. What will be the concentration of a 1.5 M H2O2 solution after 20s?
4. NO2 reacts with itself to form a dimer, in a second-order reaction.
a. Calculate the rate constant for the reaction if it takes 0.0050 s for the initial concentration of NO 2
to decrease from 0.50 M to 0.25 M.
b. How long will it take for the concentration to decrease from 0.50 M to 0.15M?
Mechanisms
1. What would be the rate law for a simple one-step reaction such as the following?
CH3Br + SH- → CH3SH + Br-1
2. Define rate-limiting step.
3. Define mechanism.
4. If a reaction does not occur in a single step, what must be known in order to write a rate law for the
reaction?
5. NO reacts with H2 according to the following equation:
2NO(g) + 2H2(g) ⇌ N2(g) + 2H2O(g)
The mechanism for the reaction involves two steps:
2NO + H2 → N2 + H2O2
H2O2 + H2 → 2H2O
What is the predicted rate law for the reaction if the first step is the rate-limiting step?
6. The disproportionation of NO to N2O and NO2 is third-order in NO.
3NO(g) ⇌ N2O(g) + NO2(g)
a. What is the rate law?
b. Which of the following mechanisms is consistent with the rate law?
i. NO + NO + NO → N2O + NO2
ii. 2NO → N2O2
(rate limiting step)
N2O2 + NO → N2O + NO2
iii. 2NO → N2O2
N2O2 + NO → N2O + NO2 (rate limiting step)
7. N2O5 decomposes to form NO2 and O2.
a. Write the balanced chemical reaction
b. This reaction is first order. Write the rate law for this reaction.
c. Show how the rate law is consistent with the following three-step mechanism for the reaction.
i. N2O5 ⇌ NO2 + NO3
ii. NO2 + NO3 → NO2 + NO + O2
iii. NO + NO3 → 2NO2
8. Hydrogen and Bromine react to form hydrogen bromide. Rate = k(H 2)(Br2)1/2. Show how the following
mechanism, in which the second equation is the rate-limiting step, is consistent with the rate law.
i. Br2 ⇌ 2Br
ii. Br + H2 → HBr + H
iii. H + Br2 → HBr + Br