The following table gives data on the adsorption of benzene...

The following table gives data on the adsorption of benzene by graphitized carbon black (P-33) at two surface coverages and two temperatures: \[ \begin{array}{ccc} v\left(\mathrm{cm}^{3} \mathrm{g}^{-1} \text {at } 25^{\circ} \mathrm{C}, 1 \mathrm{bar}\right) & 0.2 & 0.4 \\ t / \mathrm{C}^{\circ} & \multicolumn{2}{c} {\text {Pressure}(\mathrm{Pa})} \\ \hline 0 & 13 & 27 \\ 35.0 & 80 & 170 \end{array} \] Calculate the enthalpy of adsorption $\Delta_{\text {ads }} H$ at each coverage. (S. Ross and J. P. Oliver, On Physical Adsorption, p. 238. New York: Wiley-Interscience, 1964.)

The following table gives data on the adsorption of benzene by graphitized carbon black (P-33) at two surface coverages and two temperatures:
\[
\begin{array}{ccc}
v\left(\mathrm{cm}^{3} \mathrm{g}^{-1} \text {at } 25^{\circ} \mathrm{C}, 1 \mathrm{bar}\right) & 0.2 & 0.4 \\
t / \mathrm{C}^{\circ} & \multicolumn{2}{c} {\text {Pressure}(\mathrm{Pa})} \\
\hline 0 & 13 & 27 \\
35.0 & 80 & 170
\end{array}
\]
Calculate the enthalpy of adsorption $\Delta_{\text {ads }} H$ at each coverage.
(S. Ross and J. P. Oliver, On Physical Adsorption, p. 238. New York: Wiley-Interscience, 1964.)

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Key Concepts

Adsorption

Adsorption is the process by which molecules or atoms from a gas or liquid phase adhere to the surface of a solid or liquid. This phenomenon is governed by surface interactions and is central to understanding processes such as catalyst behavior and separation technologies.

Enthalpy of Adsorption

The enthalpy of adsorption refers to the heat exchange that occurs when a molecule adheres to a surface. It is usually released (exothermic process) during adsorption, and its value can indicate the strength of interaction between the adsorbate and adsorbent.

Clausius-Clapeyron Equation

The Clausius-Clapeyron equation is a thermodynamic relation that describes the change in pressure with temperature for a phase change, or in this case, an adsorption process at constant coverage. In adsorption studies, it is used to relate the equilibrium vapor pressure to the temperature, allowing for the calculation of the enthalpy of adsorption.

Temperature Dependence of Adsorption Equilibrium

Adsorption equilibrium is influenced by temperature, as variations in temperature affect the kinetic energy of molecules and the equilibrium between the adsorbed and gaseous phases. Analyzing how equilibrium pressure changes with temperature at constant surface coverage is essential for determining thermodynamic parameters like the enthalpy of adsorption.

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