Answer
75 sec
Work Step by Step
The given reaction is a first order reaction and as it takes 25 sec for it to become half of its concentration thus the half-life of this reaction.
t1/2 = 25
for the initial concentration to become 1/8th it requires 1/2 to be multiplied by 1/2 another 2 times that means we are reducing the initial concentration to 1/8th.
thus 12 * 12 * 12 = 18
thus the time = 3*25sec = 75 sec
the time for 14 to become 18 is just halving the concentration thus it will be just the half-life. that is 25 sec.
