Answer : The initial concentration of A is, 0.347 mol/L
Explanation :
Expression for rate law for first order kinetics is given by:
[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]
where,
k = rate constant = [tex]0.291s^{-1}[/tex]
t = time passed by the sample = 5 s
a = initial amount of the reactant = ?
a - x = amount left after decay process = 0.081 mol/L
Now put all the given values in above equation, we get
[tex]5=\frac{2.303}{0.291}\log\frac{a}{0.081}[/tex]
[tex]a=0.347mol/L[/tex]
Therefore, the initial concentration of A is, 0.347 mol/L
