1. For the reaction A +B --------- C + D doubling the concentration of both the reactants increases the reaction rate by 8 times and doubling the concentration of only B simply doubles the reaction rate. Find the rate law for the equation.

The rate of reaction becomes 2 times when the concentration of B is doubled, therefore rate with respect to B = 1

Now, rate of reaction becomes 8 times when concentration of both A and B is doubled.

Since, rate wr.r.t B is 1, it must be 2 w.r.t A

Hence, rate = k [A]2[B]

Putting A = 2 A and B = 2B, we can verify that rate = 8 times as follows:

Rate =  k [2A]2[2B] = 8 x k [A]2[B]

  • 74

General rate equation is. Rate =k[A]x[B]y


  1. [A]------[2A]
  2. [B]------[2B]
  3. Rate = k [2A][2B]power raised to 2 because it is second order reaction
  4. Rate = 8k[A][B]

2nd Case

  1. [B]......[2B]
  2. Rate=k[A][2B]2
  3. Rate=4k[A][B]2
  • -74
What are you looking for?