Surface Chemistry - Formula Sheet

Thermodynamics of Adsorption

\(\Delta G = \Delta H - T \Delta S\)

• \(\Delta G\): Change in Gibbs free energy (must be negative for spontaneity).
• \(\Delta H\): Change in enthalpy (negative for exothermic adsorption).
• \(T\): Absolute temperature in Kelvin.
• \(\Delta S\): Change in entropy (negative as randomness decreases during adsorption).

Freundlich Adsorption Isotherm

\(\frac{x}{m} = k P^{\frac{1}{n}}\)

• \(x\): Mass of the adsorbate.
• \(m\): Mass of the adsorbent.
• \(P\): Equilibrium pressure of the gas.
• \(k, n\): Constants depending on the nature of the adsorbent and gas at a specific temperature.

Linearized Freundlich Equation

\(\log(\frac{x}{m}) = \log k + \frac{1}{n} \log P\)

• \(\frac{1}{n}\): Slope of the straight line plot.
• \(\log k\): The y-axis intercept of the plot.

Coagulation and Valency

Coagulating Power \(\propto (Valency)^n\)

• Valency: The electrical charge of the active ion causing precipitation.
• \(n\): An exponent indicating the high sensitivity of coagulation to the ion's charge.