If the half-life (t1/2) for a first order reaction is 1 minute, then the time required for 99.9\% completion of the reaction is closest to :
- 5 minutes
- 10 minutes
- 2 minutes
- 4 minutes
Answer
(2) 10 minutes
Solution
For a first order reaction: k = 0.693t1/2 and t = 2.303k [A]0[A]
For 99.9\% completion: [A]0[A] = 1000.1 = 1000 ⇒ 1000 = 3
∴ t99.9\% = 2.303 30.693 t1/2
= 9.97 1 min
10 minutes
Answer: (2)