15. Chemical Kinetics

Stoichiometric Rate Calculations

15. Chemical Kinetics

Stoichiometric Rate Calculations

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Multiple Choice

Write the rate law for the following mechanism: Step 1: NO₂ + NO₂ → NO₃ + NO (slow)
Step 2: NO₃ → NO + O₂ (fast)

rate = k[NO₂]

rate = k[NO₃]

rate = k[NO₂]²

rate = k[NO₃][NO]

rate = k[NO][O₂]

Verified step by step guidance

Identify the slow step in the mechanism, as it determines the rate law for the overall reaction. In this case, Step 1 is the slow step: NO2 + NO2 → NO3 + NO.

Write the rate law based on the slow step. The rate law is determined by the reactants involved in the slow step. Since Step 1 involves two NO2 molecules, the rate law is: rate = k[NO2]^2.

Recognize that the fast step does not directly affect the rate law of the overall reaction, but it completes the mechanism. Step 2: NO3 → NO + O2 is fast and does not appear in the rate law.

Understand that intermediates like NO3, which are produced and consumed within the mechanism, do not appear in the rate law for the overall reaction.

Conclude that the rate law for the overall reaction is based solely on the slow step, resulting in: rate = k[NO2]^2.

2:28m

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Multiple Choice

The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. 2 K2Cr2O7 + 8 H2SO4 + 3 C2H6O → 2 Cr2(SO4)3 + 2 K2SO4 + 11 H2O If the rate of appearance of Cr2(SO4)3 is 2.10 mol/min, what is the rate of disappearance of C2H6O?

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Multiple Choice

In the Breathalyzer reaction, if the rate of appearance of Cr2(SO4)3 is 2.04 mol/min, what is the rate of disappearance of C2H6O?

Multiple Choice

Using the following data, determine the order of the reaction with respect to [NO₂^–].

Data Table for Three Experiments
Experiment	Initial [NH₄⁺]	Initial [NO₂]	Initial rate (M/s)
Experiment 1	0.24 M	0.10 M	7.2 × 10^-6 M/s
Experiment 2	0.12 M	0.10 M	3.6 × 10^-6 M/s
Experiment 3	0.12 M	0.15 M	5.4 × 10^-6 M/s

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Multiple Choice

Using the data below (also from question 6), determine the overall order of the reaction.

Data Table for Three Experiments
Experiment	Initial [NH₄⁺]	Initial [NO₂]	Initial rate (M/s)
Experiment 1	0.24 M	0.10 M	7.2 × 10^-6 M/s
Experiment 2	0.12 M	0.10 M	3.6 × 10^-6 M/s
Experiment 3	0.12 M	0.15 M	5.4 × 10^-6 M/s

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Textbook Question

(a) Consider the combustion of hydrogen, 2 H21g2 + O21g2 ¡ 2 H2O1g2. If hydrogen is burning at the rate of 0.48 mol>s, what is the rate of consumption of oxygen? What is the rate of formation of water vapor?

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Textbook Question

Ammonia is manufactured in large amounts by the reaction N21g2 + 3 H21g2S 2 NH31g2 (b) How is the rate of formation of NH3 related to the rate of consumption of N2?

Textbook Question

Chlorite is reduced by bromide in acidic solution according to the following balanced equation: ClO2 -1aq2 + 4 Br-1aq2 + 4 H+1aq2S Cl-1aq2 + 2 Br21aq2 + 2 H2O1l2 (a) If Δ3Br24>Δt = 4.8 * 10-6 M>s, what is the value of Δ3ClO2 -4>Δt during the same time interval?

Textbook Question

For each of the following gas-phase reactions, indicate how the rate of disappearance of each reactant is related to the rate of appearance of each product:

(a) H₂O₂(g) → H₂(g) + O₂(g)

(b) 2 N₂O(g) → 2 N₂(g) + O₂(g)

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Write the rate law for the following mechanism: Step 1: NO2 + NO2 → NO3 + NO (slow) Step 2: NO3 → NO + O2 (fast)

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Stoichiometric Rate Calculations practice set

Write the rate law for the following mechanism: Step 1: NO₂ + NO₂ → NO₃ + NO (slow)
Step 2: NO₃ → NO + O₂ (fast)