Question

Consider the proposed two-step reaction mechanism:
A + B + C → D (slow)
D → A + E (fast)

Which statements regarding this mechanism are true?

C. A is an intermediate because it is neither produced nor consumed during the chemical reaction.

B. A is a catalyst because it is produced in one step in the mechanism and consumed in a subsequent step.

E. D is an intermediate because it is produced in one step in the mechanism and consumed in a subsequent step.

D. A is a catalyst because it is neither produced nor consumed during the chemical reaction.

G. D is an intermediate because it is neither produced nor consumed during the chemical reaction.

H. D is a catalyst because it is neither produced nor consumed during the chemical reaction.

A. A is an intermediate because it is produced in one step in the mechanism and consumed in a subsequent step.

F. D is a catalyst because it is produced in one step in the mechanism and consumed in a subsequent step.

Answer 1

A + B + C → D (slow)
D → A + E (fast)

The statements that are true regarding this mechanism:

E. D is an intermediate because it is produced in one step in the mechanism and consumed in a subsequent step.

D. A is a catalyst because it is neither produced nor consumed during the chemical reaction.

Explanation:

Intermediate: An intermediate is a molecular entity that is formed from the reactants (or preceding intermediates) and reacts further to give the directly observed products of a chemical reaction. Most chemical reactions are stepwise, that is they take more than one elementary step to complete.

Catalyst: A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up, or catalyze.