Answer:
9.1 seconds
Explanation:
Given that for a second order reaction
1/[A]t = kt + 1/[A]o
Where [A]t= concentration at time = t= 0.340M
[A]o= initial concentration = 0.820M
k= rate constant for the reaction=0.190m-1s-1
t= time taken for the reaction (the unknown)
Hence;
(0.340)^-1 = 0.190×t + (0.820)^-1
t= (0.340)^-1 - (0.820)^-1/0.190
t= 9.1 seconds
Hence the time taken for the concentration to decrease from 0.840M to 0.340M is 9.1 seconds.