Given, the reaction 2A+B2⟶2AB is an elementary reaction.
So, rate of reaction =k[A]2[B2] Initial rate =k(a∕V)2(b/V)1 where, a and b are the number of moles of A and B and V is the volume. On reducing the volume by a factor of 3 , the concentrations of A and B2 will become 3 times Final rate =k(3a∕V)2(3b/V)132×3k(
a
V
)2(
b
V
)1=27× initial rate Hence, the rate becomes 32×3=27 times of initial rate.