The reaction A2 + 2 B → 2 BA is thought to occur by the following mechanism:

Step 1: A2 + Z → ZA2
Step 2: ZA2 + B → BA + Z + A
Step 3: A + B → BA

Which of the following statements is correct? Select one:

a. ZA2 and A are catalysts, and Z is a reaction intermediate.
b. There are no catalysts or reaction intermediates.
c. Z is a catalyst, and ZA2 and A are reaction intermediates.
d. Z, ZA2, and A are all catalysts.
e. Z, ZA2, and A are all reaction intermediates.

c. Z is a catalyst, and ZA2 and A are reaction intermediates.

Explanation:

Overall reaction is given as;

A2 + 2 B → 2 BA

Mechanism:

Step 1: A2 + Z → ZA2

Step 2: ZA2 + B → BA + Z + A

Step 3: A + B → BA

The options given are centered upon catalysts and reaction intermediates. So before proceeding, we have to understand the difference between the two and how to identify them.

A catalyst is basically a reaction booster to speed up the rate of the reaction and the reaction intermediate is an unstable, temporl species formed from the reactants before getting to the products.

The difference is given as;

Catalysts are present as reactants in the very beginning and products at the end of the reaction.

Intermediates, on the other hand, are not present in the initial reaction but are produced within one of the steps and then consumed within another step.

Following the above, we can deduce that;

Z is a catalyst because it is present as a reactant in the beginning.

ZA2 and A are a reaction intermediates because they are not present in the overall reaction but are produced and consumed in one of the steps.

Correct option is given as;

c. Z is a catalyst, and ZA2 and A are reaction intermediates.