__________ is concerned with the adsorption equilibria.

ANS:C - Freundlich equation

The Freundlich equation is an empirical relationship used to describe the adsorption of a solute onto a solid adsorbent from a liquid phase. It was formulated by Herbert Freundlich in 1906 and is widely employed in the study of adsorption processes in various fields such as chemistry, chemical engineering, environmental science, and surface science. The Freundlich equation is typically expressed as: 𝑞=𝐾⋅𝐶1/𝑛q=K⋅C1/n Where:

• 𝑞q is the amount of solute adsorbed per unit mass of adsorbent (usually in units like grams of solute per gram of adsorbent).
• 𝐶C is the equilibrium concentration of the solute in the liquid phase (usually in units like moles per liter or grams per liter).
• 𝐾K is the Freundlich constant, which represents the adsorption capacity of the adsorbent and depends on the nature of the adsorbent and the solute-solvent system.
• 𝑛n is the Freundlich exponent, which is a dimensionless parameter related to the heterogeneity of the adsorbent surface and the intensity of adsorption.

1. Nonlinear Relationship: The Freundlich equation describes a nonlinear relationship between the amount of solute adsorbed and the equilibrium concentration of the solute in the liquid phase. This nonlinearity implies that the adsorption process does not follow simple Langmuir adsorption behavior, which assumes a monolayer adsorption onto a homogeneous surface.
2. Multilayer Adsorption: Unlike the Langmuir model, which assumes monolayer adsorption, the Freundlich equation can accommodate multilayer adsorption onto heterogeneous surfaces. It accounts for the fact that adsorbate molecules can adhere to the surface at multiple sites and in multiple layers.
3. Adsorption Intensity: The Freundlich exponent 𝑛n characterizes the adsorption intensity or strength. When 𝑛n is close to 1, the adsorption is considered to be favorable and relatively uniform. As 𝑛n deviates from 1, the adsorption becomes increasingly heterogeneous, with varying affinities of adsorbate molecules for different sites on the adsorbent surface.
4. Experimental Determination: The Freundlich equation can be fitted to experimental data obtained from adsorption isotherm experiments. By plotting the amount of solute adsorbed against the equilibrium concentration and applying appropriate regression techniques, the Freundlich parameters 𝐾K and 𝑛n can be determined.