The number of seconds for the concentration to decrease to 0.13 mol for a second order reaction is calculated using the below formula
1/At =-Kt +1/Ao where At is the final concentration, Ao is the initial concentration. t = time in second while k = constant
1/0.13 =-0.13 (t) + 1/0.26
like terms together
1/0.13-1/0.26 =-0.13 t
divide both side by 0.13
T =29.6 seconds