CHEMISTRY · Single correct · AP · Chemistry · Kinetics · Kinetics
Problem
Consider the following three-step mechanism.
Step 1 A + X ⇌ AX (fast)
Step 2 AX + B → AB + X (slow)
Step 3 AB + C → ABC (fast)
Which statement best classifies species X?
(a) X is a reactant because it appears as a starting material in Step 1 and must remain in the overall balanced equation.
(b) X is an intermediate because it is produced in Step 2 and consumed in Step 3 without regeneration.
(c) X is a catalyst because it is consumed in Step 1, regenerated in Step 2, and does not appear in the overall balanced equation.
(d) X is a product because it is regenerated in Step 2 and therefore persists to the end of the reaction.