Question

If the half-life of a first-order reaction is 10 minutes, find the time required to decrease the concentration of the reactant from 0.08 M to 0.02 M.

Options

• 10 minutes

• 20 minutes

• 30 minutes

• 40 minutes

Answer 1

20 minutes

Explanation:

`t_(1/2) = 0.693/k`

k = `0.693/ (10 min)`

kt = `ln  A_0/A`

`(0.693 xx t)/10 = ln  0.08/0.02`

t = 20 minutes