[hasm273]

Hello,

I need to find the reaction rate law for the following reaction, where A and B adsorb to the catalyst and C (a gas) doesn't adsorb.

A + B + C > D + E

I started off by assuming the reaction followed Langmuir-Hinshelwood kinetics however my final rate law had concentrations of A and B on the active site (A.S/B.S) - which cannot be measured & I couldn’t eliminate. I now think my assumption of Langmuir-hinshelwood kinetics is incorrect because the reactant C does not adsorb onto the catalyst.

My main stumbling block is having 2 species adsorbing to the catalyst. I assumed the rate-determining step is the surface reaction. When I apply the pseudo‐steady‐state hypothesis and equate the non‐limiting rates to 0, I can't get an expression in terms of A or B only - as they both appear in the adsorption expression. I'm not too sure where to go from here?

Apologies if this wasn't clear - this is my only chemistry-based module so I'm a bit rusty, thanks in advance!