question_answer 55)

    A first order reaction is 50% completed in. How much time would it take for 100% completion? (a) 1.26x1015 s                    (b) 252x1014s (c) 2.52x1028 s                    (d) Infinite

Answer:

                  (d) The time taken for half the reaction to complete, i.e., the time in which the concentration of a reactant is reduced to half of its original value is called half-life period of the reaction. But it is impossible to perform 100% of the reaction. Whole of the substance never reacts because in every half-life, 50% of the substance reacts. Hence, time taken for 100% completion of a reaction is infinite.