Question

36.For the reaction A+B→P, the rate is given by:
Rate=K [A] [B]2
(a)How is the rate of reaction affected if the concentration of B is doubled?
(b) (i)What is the overall order of reaction if a is present in large excess.
(ii)A first order reaction takes 30 minutes for 50% completion.Calculate the time required for 90% completion of
the reaction.

Answer 1

Answer:

a.

(i) For a reaction, A+B→P

R1 =k[A][B]   ---------(i)

If the concentration of B is doubled,

R2 =k[A][2B] ---------(ii)

On dividing (i) and (ii)

R1/R2 = k[A][B]^2 / k[A][2B]^2

R1/R2 = B^2/4B^2

R2 = 4R1

The rate of reaction will be four times the initial rate.

(ii) If A is present in large excess, then the rate of the reaction will be independent of A and will depend only on the concentration of B. The overall rate of the reaction will be 2.        

(b)

K=0.693/30=0.0231

The time required to complete 90% reaction,

t=(2.303/.0231)×log(100/10)=100 minutes