It is a first order isomerisation reaction. Integrated rate law for 1 st order reaction is kt=ln
[A]0
[A]t
. . . (i) Here, k= rate constant [A]0= initial concentration [A]t= concentration at time ′t′ Given, k=3.3×10−4s−1 [A]0=100⇒[A]t=100−40=60 Put values in Eq. (i), we get 3.3×10−4s−1×t=ln