For a first order reaction A → B, the reaction rate at reactant concentration of 0.01 M is found to be 2.0 x 10^-5 mol L^-1 s^-1. The half life period of the reaction is :

For a first-order reaction, the rate of reaction (r) is given by r = k[A], where k is the rate constant and [A] is the concentration of the reactant. Given that the rate at a concentration of 0.01 M is 2.0 x 10^-5 mol L^-1 s^-1, we can find the rate constant k: 2.0 x 10^-5 = k * 0.01, which gives k = 2.0 x 10^-5 / 0.01 = 2.0 x 10^-3 s^-1. The half-life (t1/2) of a first-order reaction is given by t1/2 = ln(2) / k = 0.693 / k. Substituting the value of k, we get t1/2 = 0.693 / (2.0 x 10^-3) = 346.5 s, which is closest to option D, 347 s.