Answer: 8.38 seconds
Explanation:
Integrated rate law for second order kinetics is given by:
[tex]\frac{1}{a}=kt+\frac{1}{a_0}[/tex]
[tex]a_0[/tex] = initial concentartion = 0.860 M
a= concentration left after time t = 0.230 M
k = rate constant =[tex]0.380M^{-1}s^{-1}[/tex]
[tex]\frac{1}{0.860}=0.380\times t+\frac{1}{0.230 }[/tex]
[tex]t=8.38s[/tex]
Thus it will take 8.38 seconds for the concentration of A to decrease from 0.860 M to 0.230 M .