Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H⁺ + H₂O₂ H₂O⁺-OH (rapid equilibrium)
H₂O⁺-OH + Br^- → HOBr + H₂O (slow)
HOBr + H⁺ + Br^- → Br₂ + H₂O (fast)
Which of the following rate laws is consistent with the mechanism?

Question

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H⁺ + H₂O₂

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H<sup>+</sup> + H<sub>2</sub>O<sub>2</sub> H<sub>2</sub>O<sup>+</sup>-OH (rapid equilibrium) H<sub>2</sub>O<sup>+</sup>-OH + Br<sup>-</sup> → HOBr + H<sub>2</sub>O (slow) HOBr + H<sup>+</sup> + Br<sup>-</sup> → Br<sub>2</sub> + H<sub>2</sub>O (fast) Which of the following rate laws is consistent with the mechanism? A) Rate = k[H<sub>2</sub>O<sub>2</sub>][H<sup>+</sup>]<sup>2</sup>[Br<sup>-</sup>] B) Rate = k[H<sub>2</sub>O+-OH][Br<sup>-</sup>] C) Rate = k[H<sub>2</sub>O<sub>2</sub>][H<sup>+</sup>][Br<sup>-</sup>] D) Rate = k[HOBr][H<sup>+</sup>][Br<sup>-</sup>][H<sub>2</sub>O<sub>2</sub>] E) Rate = k[Br<sup>-</sup>]

H₂O⁺-OH (rapid equilibrium)
H₂O⁺-OH + Br^- → HOBr + H₂O (slow)
HOBr + H⁺ + Br^- → Br₂ + H₂O (fast)
Which of the following rate laws is consistent with the mechanism?

Quizplus · Accepted Answer

The rate-determining step involves the simultaneous collision of three species: H₂O⁺, Br^-, and H+. Therefore, the rate law should include all three reactants, which is consistent with choice C. The other choices do not include all three reactants or include species that are not involved in the rate-determining step.

Consider the Following Mechanism for the Oxidation of Bromide Ions