A 1st order reaction, where

Question

A-> products

has a rate constant of 1.56x 10^7 s^-1. At some time, a concentration of 1.06 x 10^-6 M of species A is introduced into the reactor. How long does it take for the concentration of A to fall by a factor of 8?

Answer 1

Use the integrated rate equation for a first order reaction:

ln{[A]/[A]0} = -kt

The problem tells you that [A]/[A]0 = 1/8, so substitute in for k and solve for t:

ln(1/8) = -1.56 x 10^7 s^-1 (t)

t = 1.33 x 10^-7 s