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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry, 4th edition.

Problem 13.34.

In the reaction, A products, with the initial concentration [A]0 = 1.512 M, [A] is found to be 1.496 M at t = 30 s. With the initial concentration [A]0 = 2.584 M, [A] is found to be 2.552 M at t = 1 min. What is the order of this reaction?


First, find the rate of reaction in each experiment, being sure to be consistent in units. Then use the Method of Initial rates to find the order of reaction.


[A]0 (M)

[A] (M) at t (s)

Rate (M s–1)



1.496 at 30 s



2.552 at 60 s

Since the rates are the same for both experiments, the reaction must be zero order. Mathematically:

, which can only be true for m = 0.