Question

After 62.0 min, 33.0% of a compound has decomposed. What is the half-life of this reaction assuming first-order kinetics?

Answer 1

The first thing you need to do, is to find the half life which is ( = (ln2)/k). To find it, we have to use the rate constant k
The first order reaction has to be like this  :$ln[A] = ln[A]o -kt at time t= 62 min$
Then :$[A] = 67% [A]o or 0.67[A]o$
Then substitute these value and kind the k value.
After substitution you can easily find what you were asked to find.