The half-life for the second-order decomposition of HI is 15.4 s when the initial concentration of HI is 0.67 M.What is the rate constant for this reaction?

Question

Quizplus · Accepted Answer

Using the formula for the rate constant of a second-order reaction:

k = 1/t(1/([HI]0) - 1/[HI])

We know the half-life (t1/2) and can solve for the rate constant:

t1/2 = (ln 2)/k = 15.4 s

k = (ln 2)/t1/2 = (0.693/15.4 s) = 4.49x10^-2 M^-1s^-1

Rounded to two significant figures, this is 9.7x10^-3 M^-1s^-1, which corresponds to choice C.

The Half-Life for the Second-Order Decomposition of HI Is 15