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?

Select one:
a. Rate = k [H2O+-OH][Br-]
b. Rate = k[Br-]
c. Rate = k[HOBr][H+][Br-][H2O2]
d. Rate = k[H2O2][H+][Br-]
e. Rate = k[H2O2][H+]2[Br-]

a. Rate = k [H2O+-OH][Br-]

Explanation:

For a reaction:

nA+xB→C+D

The rate of the reaction is:

Rate = [A]ⁿ[B]ˣ

Now, in a mechanism, the rate of the reaction depends of the slow step. In the problem:

H2O+-OH + Br-→ HOBr + H2O

And the rate is:

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.