Which of the following is the correct rate law for the elementary reaction: O3(g) + O(g) → 2O2(g)?

• A. rate = k[O]
• B. rate = k[O3]^2
• C. rate = k[O2]^2
• D. rate = k[O3][O]

Answer: (D)

Verified step by step guidance

1. Identify that the reaction given is an elementary reaction, which means the rate law can be written directly from the molecularity of the reaction step.
2. Write the balanced elementary reaction: \(\mathrm{O_3(g) + O(g) \rightarrow 2O_2(g)}\).
3. Since the reaction involves one molecule of \(\mathrm{O_3}\) and one atom of \(\mathrm{O}\) colliding, the rate law depends on the concentration of both reactants.
4. Express the rate law as: \(\text{rate} = k[\mathrm{O_3}][\mathrm{O}]\), where \(k\) is the rate constant.
5. Confirm that the rate law matches the stoichiometry of the elementary step, and that no other species (like \(\mathrm{O_2}\)) appear in the rate law because they are products, not reactants.