For a reaction A+B→product, it was found that rate of reaction increases four times if concentration of ‘A’ is doubled, but the rate of reaction remains unaffected, If concentration of ‘B’ is doubled. Hence, the rate law for the reaction is

Let the rate of reaction depends on Xth power of [A]. Then r1=k[A]x and r2=k[2A]x∴r1r2=[A]x[2A]x=14=(12)2(∵ r2=4r1)∴ x=2. As the reaction rate does not depend upon the concentration of B. Hence, the correct rate law will be rate =K[A]2[B]o or =K[A]2