For the reaction `A+2BrarrC+D` , the rate of the reaction= `k[A][B]^(2)` where k = rate rate constant. How can the reaction be converted to
a pseudo first order and

Explanation

1) If B is taken in a large excess compared to the of A. then the change in concentration of B takes place to a negligible extent in comparison to A during the reaction, i.e. the concentration of B remains almost constant.
Hence , reaction -rate `=k[A][B]^(2)=k'[A](k'=k[B]^(2)= "constant")` and the reaction becomes a pseudo first order reaction.