Question

The rate constant of a first-order process that has a half-life of 3.50 min is __________ s-1.

Answer 1

The process may be represented by
$A(t) = A_{0}\, e^{-kt}$
where k =  the rate constant (1/s)
            t = time, s

At half life, A = (1/2) A₀, and t = 3.5*60 = 210s.
Therefore
$e^{-210k}= \frac{1}{2}$
-210 k = ln(0.5)
k = -ln(0.5)/210 = 0.0033

Answer:  0.0033 1/s  or  3.3x10⁻³ s⁻¹