The rate constant for the first order decomposition of A at 500oC is 9.2 x 10-3 s-1. how long will it take for 90.8% of a 0.500 M sample of A to decompose? Question options:

For this problem, we assume a first-order kinetics which has a kinetics expression written as:

ln (Ca/Cao) = - kt

We use this formula to solve for time, t. First we list the needed values,

k = 9.2 x 10-3 s-1

Cao = 0.500 M

Xa = 90.8% = 1 - (Ca/Cao)

Ca = 0.046 M

ln (0.046/0.500) = - 9.2 x 10-3 s-1 (t)

t = 259.34 s