9-7. A gas-solid catalytic reaction of the type A + B + C is believed to occur by a molecule of B in the gas phase reacting with a molecule of A adsorbed on the catalyst surface. Preliminary experimental studies indicate that both external and internal diffusional resistances are negligible. Also, the equilibrium con- stant for the homogeneous reaction K = (pc/PP), is very large. The rate of reaction per gram of catalyst is measured at varying total pressures, but constant composition of reactants. The results show a linear relationship between r and p, all the way down to pressures approaching zero. What con- clusions may be drawn from these data concerning the controlling steps in the reaction