Answer: It takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.
Explanation:
Integrated rate law for second order kinetics is given by:
[tex]\frac{1}{a}=kt+\frac{1}{a_0}[/tex]
k = rate constant = [tex]0.610M^{-1}s^{-1}[/tex]
[tex]a_0[/tex] = initial concentration = 0.860 M
a= concentration left after time t = 0.260 M
[tex]\frac{1}{0.260}=0.860\times t+\frac{1}{0.860}[/tex]
[tex]t=3.120s[/tex]
Thus it takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.