alleryStart learning →Ozone decomposes by the two step mechanism O3 giving O2 + O, then O + O3 giving 2O2. Which species is an intermediate?
AThe O3 reactant
BThe free O atom
CThe O2 product
DThe O3 and the O2
Answer & Solution
Correct answer: B. The free O atom
1. An intermediate is produced in one step and consumed in a later one, so it never appears in the overall equation.
2. The oxygen atom is made in the first step and eaten in the second, which fits exactly.
3. Adding the steps gives 2O3 giving 3O2, and the O atom has cancelled out.
4. O3 is a reactant and O2 is a product; both survive into the overall equation, so neither is an intermediate.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.6 Reaction Mechanisms_
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