The half-life of a zero order reaction ([A] = [A]_o

Question

The half-life of a zero order reaction ([A] = [A]_o - k t) is 3.15 sec for an initial concentration ([A]_o) of 0.500 M . What is the rate constant for this reaction in mol/L × s?

Quizplus · Accepted Answer

The half-life equation for a zero-order reaction is:

t1/2 = [A]0/2k

We are given t1/2 = 3.15 s and [A]0 = 0.500 M.

Plugging these values into the equation, we can solve for k:

3.15 s = 0.500 M / 2k

2k = 0.500 M / 3.15 s

k = (0.500 M / 3.15 s) / 2

k = 0.0794 M/s = 7.94 × 10^-2 mol/L × s

Rounding this value to three significant figures gives a rate constant of 7.94 × 10^-2 mol/L × s, which corresponds to choice C.

The Half-Life of a Zero Order Reaction ([A] = [A]o