Ch 13 - 103E

Chapter 13, Problem 103E

(choose chapter or problem)

Consider the gas-phase reaction:

        \(\mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) \longrightarrow 2 \mathrm{\ HI}(g)\)

The reaction was experimentally determined to be first order in \(\mathrm{H}_{2}\) and first order in \(\mathrm{I}_{2}\). Consider the proposed mechanisms.

Proposed mechanism I:

         \(\mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) \longrightarrow 2 \mathrm{\ HI}(\mathrm{g})\)                Single Step

Proposed mechanism II:

         \(\mathrm{I}_{2}(\mathrm{g}) \stackrel{k_{1}}{\underset{k_{-1}}{\rightleftharpoons}} 2 \mathrm{\ I}(\mathrm{g})\)                                     Fast

        \(\mathrm{H}_{2}(\mathrm{g})+2 \mathrm{\ I}(\mathrm{g}) \underset{k_{2}}{\longrightarrow} 2 \mathrm{\ HI}(\mathrm{g})\)               Slow

a. Show that both of the proposed mechanisms are valid.

b. What kind of experimental evidence might lead you to favor mechanism II over mechanism I?