Answer:
Option B
Explanation:
For the elementary reaction, M→N
Rate law can be written as
Rate ∝[M]n
Rate = k[M]n ...........(i)
When we double the concentration of [M] , rate becomes 8 times , hence new rate law can be written as
8×Rate=k[2M]n ...........(ii)
Rate8×Rate=k[M]nk[2M]n
⇒ 18=1[2]n⇒[2]n=8=[2]3
n=3
Hence, (b) is the correct choice.