A first-order reaction was started with a decimolar solution of the reactant, `8` minutes and `20 `seconds later its concentration was found to `M//100`. So the rate of the raction is

Options

A. `2.303 xx 10^(-5) sec^(-1)`
B. `2.303 xx 10^(-4) sec^(-1)`
C. `4.606 xx 10^(-3) sec^(-1)`
D. `2.606 xx 10^(-5) sec^(-1)`

Answer

C

Explanation

For first order reaction `K = (2.303)/(t)"log"(a)/(a-x)`
Given: `a = (1)/(10) = .1m` ,
`a-x = (1)/(100) = .01m, t = 500sec`
`:. K = (2.303)/(500)"log"(.10)/(.01) = (2.303)/(500) log10`
`= (2.303)/(500) = 0.004606 = 4.6 xx 10^(-3) sec^(-1)`