In a reaction if the concentration of reactant A is tripled, the rate of reaction becomes twenty seven times. What is the order of the reaction?

Suppose reactant A forms the product B. Then the reaction can be written as

A → B

Rate of the reaction is given by

Rate₁= k[A]^x …………………..i)

x is equal to the order of the reaction.

When A is tripled rate of reaction becomes 27 times that is,

Rate₂ = k [3A]^x = 27 Rate₁ ………………………ii)

Dividing equation i) and ii)

Rate₁/ 27Rate₁ = k [A]^x/ k[3A]^x

1/27 = [1/3]^x

x = 3

Order of the reaction is 3.