Question

In a first-order reaction, the half-life is 139 minutes. What is the rate constant?

a. 8.31 x 10-5 s-1
b. 5770 s-1
c. 0.299 s-1
d. 4.99 x10-3s-1
e. 1.20 x 10-4s-1

Answer 1

a. 8.31 x 10-5 s-1

Step-by-step explanation:

The general first-order reaction is:

ln[A] = ln[A]₀ -kt

Where [A] is acutal concentration of reactant, initial concentration is [A]₀, k is rate constant and t is time pass

And the equation of the half-life, t 1/2, is:

`t_(1/2) = (ln 2)/(K)`

Has half-life is 139min:

139min * (60s / 1min) = 8340s

`t_(1/2) = (ln 2)/(8340s)`

Half-life is 8.31x10⁻⁵ s⁻¹

a. 8.31 x 10-5 s-1