Multiple Choice
Given the reaction 4 A → 3 B, if the rate of formation of B is 7 mol L⁻¹ sec⁻¹, what is the rate of depletion of A?
15. Chemical Kinetics
Stoichiometric Rate Calculations
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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
A
0
B
½
C
1
D
2
E
3
Verified step by step guidance1
Identify the rate law expression for the reaction, which is typically in the form: Rate = k[NH4+]^m[NO2-]^n, where k is the rate constant, m is the order with respect to NH4+, and n is the order with respect to NO2-.
Examine the data from the experiments to determine how changes in the concentration of NO2- affect the initial rate of the reaction, while keeping the concentration of NH4+ constant.
Compare Experiment 1 and Experiment 2: The concentration of NH4+ is halved from 0.24 M to 0.12 M, while the concentration of NO2- remains constant at 0.10 M. Observe that the initial rate is also halved from 7.2 × 10^-6 M/s to 3.6 × 10^-6 M/s. This suggests that the reaction is first order with respect to NH4+.
Compare Experiment 2 and Experiment 3: The concentration of NH4+ remains constant at 0.12 M, while the concentration of NO2- increases from 0.10 M to 0.15 M. Observe that the initial rate increases from 3.6 × 10^-6 M/s to 5.4 × 10^-6 M/s. Calculate the factor by which the concentration of NO2- increases and the factor by which the rate increases to determine the order with respect to NO2-.
Use the relationship between the change in concentration and the change in rate to solve for n in the rate law expression. If the rate increases by the same factor as the concentration, the reaction is first order with respect to NO2-. If the rate increases by a greater factor, the reaction may be of higher order.
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