A second order reaction requires 70 min to change the concentration of reactants from 0.08 M to 0.01 M. The time required to become 0.04 M = 2x min. Find the value of x.

For second order reaction:[R]initial =0.08,M;[R]final =0.01Mx=0.08−0.01=0.07M∴(a−x)=0.08−0.07=0.01Mk2=1t⋅xa(a−x) =170min×0.07M0.08M×0.01M     . . .(i)Now, time required to become concentration : 0.04 M.i.e., x = 0.04 Mk2=1t×0.04M0.08M×(0.08−0.04)M         . . . (ii)From Eqs. (i) and (ii) 0.0770×0.08×0.01=0.04t×0.08×0.04t=10min=2xmin∴x=5min