A hypothetical reaction `A_(2) + B_(2) rarr 2AB` follows the mechanism as given below:
`A_(2) hArr A+A ("fast")`
`A+B_(2) rarr AB+B` (slow)
`A+B rarr AB` (fast)
The order of the overall reaction is

Options

A. 2
B. 1
C. `3//2`
D. zero

Answer

C

Explanation

`r=K[A][B_(2)]`
and `K_(c)=([A][A])/([A_(2)])or[A]=K_(c)^(1//2)[A]^(1//2)`
Thus `r=K.K_(c)^(1//2)[A_(2)]^(1//2)[B_(2)]`
`=K^(1)[A]^(1//2)[B_(2)]or `order is `3//2`