A graph between the amount adsorbed \((\mathrm{x} / \mathrm{m})\) and temperature at a constant pressure is called: (a) Adsorption isobar (b) Adsorption isostere (c) Adsorption isochore (d) Adsorption isotherm

Adsorption is a process where molecules of a fluid (gas or liquid) accumulate on the surface of a solid or liquid (called an adsorbent), forming a molecular or atomic film. This phenomenon can typically be observed in systems such as activated charcoal filtering water impurities or gases adhering to metallic surfaces.

The key factors affecting adsorption include the nature of the adsorbent and adsorbate, surface area, temperature, and pressure. Generally, increasing surface area and pressure, or decreasing temperature, enhance adsorption.

For students tackling problems on adsorption, it's important to understand that during this process, only a surface interaction is involved, distinguishing it from absorption where the fluid permeates into the solid's bulk.

Chemical equilibrium is a state in a chemical reaction where the rates of the forward and reverse reactions are equal, resulting in no net change in the concentration of reactants and products over time. It’s crucial in physical chemistry because it can define the outcome of reactions and the stability of substances under different conditions.

An equilibrium state does not mean that the reactants and products are equal in concentration, but that their ratios do not change. The equilibrium constant (\(K\textsubscript{eq}\)) gives the ratio of product concentrations to reactant concentrations, each raised to the power of their coefficients from the balanced equation.

In the context of adsorption, the equilibrium would describe the point at which the rate of adsorption equals the rate of desorption, indicating that the amount of adsorbate on the adsorbent's surface remains constant over time.

Physical chemistry is the branch of chemistry that deals with how matter behaves on a molecular and atomic level and how chemical reactions occur. This field is fundamental for understanding concepts such as the rates of reactions, energy transfer, and the physical structure of molecules.

Regarding adsorption phenomena, physical chemistry provides insight into the forces involved, such as Van der Waals forces or chemical bonding. It uses mathematical models to represent and predict changes in systems, like the adsorption isobar, which plays a crucial part in explaining how the amount of adsorbed material varies with temperature at a constant pressure.