Chapter 6, Problem 6.29P

Interpretation Introduction

Interpretation:

With the assumption that the adsorption follows the Langmuir isotherm, the order of the $HI$ decomposition reaction on each of the two metal surfaces has to be predicted.

Concept Introduction:

Adsorption: A molecule (adsorbate) that forms a bond to the surface (adsorbent).

Associative Adsorption: A gas molecule adsorbs without fragmentation.

Dissociative Adsorption: A gas molecule adsorbs and fragmentation occurs.

Langmuir adsorption: The isotherm is based on the characteristic assumptions that only monomolecular adsorption takes place, adsorption is localized and the heat of adsorption is independent.

Langmuir equation: $p/V=p/V_m+a{V}_m$

Langmuir rate equation,

  $\begin{array}{l}{R}_{ad}\alpha P_A\left(1-\theta \right)\\ =K_{ad}{P}_A\left(1-\theta \right)\end{array}$

Where,

  $\begin{array}{l}{R}_{ad}=Rateofadsorption\\ P_A=\mathrm{Pr}essureofthegas\\ \theta =fractionofsurfacesite\text{covered}\\ {\text{k}}_{ad}=rate\text{constant}\text{for}\text{adsorption}\\ \left(1-\theta \right)=Surfacesiteremainvacantforadsorption\\ k_{de}=Rate\text{constant}\text{for}\text{desorption}\end{array}$