A flask is filled with equal moles of A and B . The half lives of A and B are 100 s and 50 s respectively and are independent of the initial concentration. The time required for the concentration of A to be four times that of B is____ s . (Given : ln 2 = 0 . 693 )

Step-by-step solution

For first order reaction k = 0 . 693 t 1 2 A = 4 B A 0 e - k A t = 4 B 0 e - k B t ∵ as A 0 = B 0 ; e - k A t = 4 e - k B t - k A t = ln 4 - k B t ∴   t k B - k A = 2 ln 2 t = 2 × 0 . 693 0 . 693 50 - 0 . 693 100 = 2 × 100 2 - 1 = 200 sec