Langmuir isotherms are generated for each component in a binary gas-phase mixture of and . You can vary the heats of adsorption of each component, the temperature, and the ratio of partial pressures. The molecules compete for adsorption sites, and this is taken into account in the form of the Langmuir isotherm; it is assumed that the mixture is ideal. You can vary the relative number of sites per molecule to account for larger molecules occupying more surface area than smaller molecules. The Langmuir isotherm for molecule has the form , where , , and .