Enhancer 2 The time taken for a first order reaction is to reduce the initial concentration by a factor of 1/4 is 20 minutes. The time required for the reduction of initial concentration by a factor of 1/16 and rate constant for this reaction are (a) 40 min, 1.606 x 10- (b) 20 min, 2.6 x 10-2 (c) 10 min, 1.606 x 10-2 (d) 25 min, 1.606 x 10-3