Given the following reaction mechanism:Step 1: NO_2 + F_2 → NO_2F + F (slow)Step 2: F + NO_2 → NO_2F (fast)Which elementary step in the proposed mechanism is the rate-limiting step?

• A. Both steps are equally rate-limiting
• B. Neither step is rate-limiting
• C. Step 1: NO_2 + F_2 → NO_2F + F
• D. Step 2: F + NO_2 → NO_2F

Answer: (C)

Verified step by step guidance

1. Understand that the rate-limiting step in a reaction mechanism is the slowest elementary step, which controls the overall reaction rate.
2. Examine the given mechanism: Step 1 is labeled as 'slow' and Step 2 as 'fast', indicating their relative speeds.
3. Since Step 1 is the slow step, it acts as the bottleneck for the reaction, limiting how fast the overall reaction proceeds.
4. Step 2, being fast, occurs quickly after the rate-limiting step and does not control the overall rate.
5. Therefore, identify Step 1: \(\mathrm{NO_2 + F_2 \rightarrow NO_2F + F}\) as the rate-limiting step.