The rate constant k of a first-order reaction can be calculated using the half-life t1/2 with the following equation:k = ln 2 / t1/2Given that the half-life t1/2 is 10 seconds, we can calculate the rate constant k as follows:k = ln 2 / 10k 0.0693 sThe rate constant of the first-order reaction is approximately 0.0693 s. Note that the initial concentration is not needed to calculate the rate constant for a first-order reaction.