Ethylene hydrogenation The hydrogenation of ethylene to hydrogen is found experimentally to follow the reaction orders given in the following table 341. 270 Chemical Kinetics Rh Catalyst Order in H2Order in CH4 0.85 -0.74 0.95 -0.59 0.55 -0.19 Ru The following steps have been suggested for the catalytic reaction mecha- nism (39. p.53). In this mechanism ethylene adsorbs associatively and H2 adsorbs dissociatively. There is a stepwise addition of adsorbed hydrogen to form an adsorbed ethyl group, C2H5 ads, and then adsorbed ethane, CyH6ynds. CH4 + S C Heads H2 + 25 2Hads C2H4.ads + Heds C2Hs ads +S CH5.ds + Hade C2H6,ads + S CzH6, ads CzH. where Sis a vacant surface site. The rate of the formation of ethane is that of the rate limiting surface hydrogenation step. There are two choices. For Scheme I, the rate limiting step is Reaction 3. For Scheme II, the rate limiting step is Reaction 4. 1. Develop a rate expression for the rate of ethane formation for Scheme 1. Let Reaction 3 be the rate-limiting step and assume all other reactions are at equilibrium. Assume that adsorptionfrom the gas phase follows a Langmuir adsorption isotherm. Neglect the reverse of Reaction 3. When performing a site balance, assume the surface is either vacant or covered with adsorbed ethylene, i. e., the coverage of ethyl, atomic hydrogen and adsorbed ethane are negligibly small 2. Develop a rate expression for the rate of ethane formation for Scheme 11. Let Reaction 4 be the rate-limiting step and assume all other reactions are at equilibrium. Assume that adsorption from the gas phase follows a Langmuir adsorption isotherm Neglect the reverse of Reaction 4. When performing a site balance, assume the surface is either vacant or covered with adsorbed ethylene and ethyl, i. e, the coverage of atomic hydrogen and adsorbed ethane are negligibly small 3. Based on the experimental data listed in the table, is Schemelor ll the more probable mechanism and why?