question_answer 18)

A reaction is first order in A and second order in B. (i) Write differential rate equation. (ii) How is the rate affected when the concentration of B is tripled? (iii) How is the rate affected when the concentration of both A and B is doubled?

Answer:

(i) r = k [A]1                                                              ?. (1) r = k [B]2                                                                                              ?. (2) differential rate equation is r = k [A]1 [B]2                                                                                 ?. (3) (ii) When conc. of B is tripled, r' = k [A]1 [3B]2                                                                            ?. (4) Divide (4) by (3)   r? = 9r. Thus, rate becomes 9 times. (iii) When conc. of both A and B is doubled, r' = k [2A]1 [2B]2                                                ?. (5) Divide (5) by (3),              Thus, rate becomes 8 times.