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

Problem 13.38.

A first order reaction, A products, has a rate of reaction of 0.00250 M s–1 when [A] = 0.484 M. (a) What is the rate constant, k, for this reaction? (b) Does t3/4 depend on the initial concentration? Does t4/5? Explain.






Answer:

(a) For a first order reaction, Rate = k[A]. Since the rate and concentration are known, solving the equation for k gives the required answer.
k = Rate/[A] = 0.00250 M s–1/0.0484 M = 5.17 × 10–3 s–1.

(b) Neither t3/4 nor t4/5 depend upon intial concentration because this is a first order reaction, which means that the time associated reaction is simply related to the rate constant.