Answer:
This is because the half life of second order reactions is inversely proportional to the initial concentration of the reactant.
Step-by-step explanation:
The equation to half life in the second order reactions is given by:
t1/2=1/[A]initial
From the equation, you can see that as the initial concentration of A increases the denominator also increases ,thus overall value (t1/2) decreases.
Hope this helps:)