NEET-XII-Chemistry
Previous Year Paper year:2017
- #63If the rate constant for a first order reaction
is k, the time (t) required for the completion
of 99% of the reaction is given by:
(1) t = 0.693/k
(2) t = 6.909/k
(3) t = 4.606/k
(4) t = 2.303/kdigAnsr: 3Ans : ( 3 )
Sol. First order rate constant is given as,
= 0
t
[A ]2.303
k log
t [A]
99% completed reaction,
= 2.303 100k log
t 1
= 22.303 log10
t
= ï‚´2.303k 2log10
t
= ï‚´ =2.303 4.606t 2
k k
= 4.606t
k