The following results were obtained during kinetic studies of the reaction, `2A +Brarr` Products

The time (in minutes) required to consume half of A is:

Options

A. 1
B. 10
C. 100
D. 5

Answer

D

Explanation

On changing the concentration of B, there is no effect on the initial rate of the reaction.
However, on doubling the conc. of A, the reaction rate doubled.
`therefore` The reaction must be first order w.r.t. A.
`R=k[A]^(x) [B]^(y)`
`6.93xx10^(-3) =k[0.10]^(x) [0.1]^(y)`
`6.93xx10^(-3) = k[0.10]^(x) [0.25]^(y)`
`1.380xx10^(-2) =k [0.20]^(x) [0.30]^(y)" "therefore x=1, y=0`
Also, `k=(6.93xx10^(-3))/(0.1) =6.93xx10^(-2)`
`t_(0.5) =(0.693)/(2k) =(0.693)/(2xx6.93xx10^(-2))=5`