1/2 t for a zero order reaction is …(I)… proportional to the initial concentration of the reactants and …(II)… proportional to the rate constant. Choose the correct words to fill up the blanks (I) and (II) respectively from the options given below. (a) (I) inversely (II) directly (b) (I) directly (II) directly (c) (I) inversely (II) inversely (d) (I) directly (II) inversely Ans. (d) Sol. t1/2 for a zero order reaction is directly proportional to the initial concentration of the reactants and inversely proportional to the rate constant.