If 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 :

Options

A. `t = 0.693`/k
B. `t=6.909`/k
C. `t=4.606`/k
D. `t=2.303`/k

Answer

C

Explanation

First order rate constant is given as,
`k = (2.303)/( t) log"" ([A_0])/( [A]_t)`
`99%` completion of reaction,
`k = (2.303)/( t) log"" (100)/( 1)`
`k = (2.303)/( t) xx 2 log10`
`t = (2.303)/( k) xx 2`
`t = (4.606)/( k)`