After 56.0 min, 40.0% of a compound has decomposed. What is the half‑life of this reaction assuming first‑order kinetics?

Go ahead and plug in the percentages and time to find the answer.

Explanation:

The amount of a substance with half-life h, that remains after time t is 0.5t/h

Since 26% has decomposed, 74% remains.

So. 74 = 0.580/h

ln. 74 = (80/h) ln 0.5

h/80 = ln 0.5 / ln. 74

h = 80 ln 0.5 / ln. 74

h = 184.16 minutes