After 43.0 minutes, 34.0% of compound decomposed. What is the half-life of this reaction assuming first order kinetics?

34% decomposition means that 66% of the compound remained, meaning the ratio of current to initial concentration after 43 minutes was 0.66. The decomposition equation:

ln[A] = ln[Ao] - kt

ln ([A] / [Ao]) = - kt

Now, we substitute the given values:

ln (0.66) = - k (43)

k = 9.66 x 10⁻³

half life = ln (2) / k

half life = 71.8 minutes.