= Solution
Dividing the total adsorbed population by the number of underlying <adsorption sites> gives
$$
\boxed{\theta_{\rm tot}=\frac{N_{\rm ads}}{M}=\frac{bp}{1-bp}},\qquad
\boxed{b=K_{\rm ads}=\frac{k_a}{k_d}},\qquad 0\leq bp<1.
$$
This multilayer uptake can exceed one because it is a mean column height. The occupied-site fraction remains $1-\theta_0=bp<1$. If each layer has the same <binding energy> and microscopic states assumed in the single-layer calculation, the corresponding thermodynamic expression for $b$ is also the one obtained there; the kinetic ratio is the definition supplied by this multilayer model.
Back to article page
