The irreversible, gas-phase reaction 2A → B + C is conducted over a solid catalyst. The reaction may be considered isothermal. The following reaction mechanism is proposed, where S represents a surface site.
- A + S ↔ A-S
- A-S + A-S → B-S + C + S
- B-S ↔ B + S
It is proposed that step 2 is rate-determining and irreversible, whereas steps 1 and 3 are equillibrated.
a. Based on the propsed mechanism, derive the Langmuir-Hinshelwood rate expression for the reaction.
b. Experiments with a differential reactor have been used to measure the rate of reaction. The results are shown below. Are the data consistent with the proposed mechanism? Under the experimental conditions, do you expect that the surface mainly consists of vacant sites, sites with adsorbed A, sites with adsorbed B, or sites with adsorbed C? Justify your answers.