The time for half-life period of a certain reaction, A→products is 1 h. When the initial concentration of the reactant ‘A’ is 2.0 mol L−1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L−1, if it is a zero order reaction?

Half-life for a zero-order reaction is given by t1/2=[A0]2k[where [A0]=initial concentration of reactant]⇒k0=[A]02t1/2=2.0 mol L−12×1 h=1.0 mol L−1 h−1Rate constant for a zero-order reaction is given by k=1t[(A0)−(A)]⇒t=1k[(A0)−(A)]t=(0.50)−(0.25)mol L−11 mol L−1 h−1⇒ t=0.25 h                   ORt1t2=a2a1 1t2=0.52 t2=0.25hrs