A reactant decomposes with a half-life of 187 s when its initial concentration is 0.269 M.

Question

When the initial concentration is 0.577 M, this same reactant decomposes with the same half-life of 187 s. What is the order of the reaction? What is the value and unit of the rate constant for this reaction?

Answer 1

Since the half life is the same regardless of the concentration, this tells us that this is a first order reaction.

Since it is a first order reaction, we can write t1/2 = ln 2/k = 0.693/2

187s = 0.693/k

k = 0.693/187s

k = 3.7x10^-3 s^-1