Correct option (c) Rate = k[B]3
Explanation :
A + B → C,
Let rate = k(A)x(B)y
where order of reaction is (x + y).
Putting the values of exp. 1, 2, and 3, we get
following equations.
Keeping [A] constant, [B] is doubled, rate becomes 8 times.
Dividing eq. (iii) by eq. (i), we get
Keeping [B] constant, [A] is doubled, rate remains unaffected. Hence rate is independent of [A]. rate ∝ [B]3.