Question

Calculate half-life for first-order reaction if 68% of a substance is reacted within 66 s.

Answer 1

k the rate constant in order to get the half-life.

Given 68% reacted → 32% remains:

ln A= −kt + ln A• → ln 0.32 = −k×66s + ln1 → k − 0.01726s − 1 ln A = −kt + ln A• → ln 0.32 = −k × 66s + ln 1 → k − 0.01726s − 1

For a first order reaction,  t1/2 = ln 2 k t 1/2 = ln 2 k =0.6930 . 01762
=0.6930 . 01762s =39.3s