Final answer:
The Langmuir plot of n-equivalent binding sites is a straight line, which is a graphical representation of the Langmuir adsorption model when the reciprocal of coverage is plotted against the reciprocal of pressure or concentration. The correct answer is (a) A straight line.
Step-by-step explanation:
The Langmuir plot of n-equivalent binding sites is a graphical representation of the Langmuir adsorption model. According to this model, the adsorption of molecules on a surface with a finite number of equivalent binding sites results in a relationship given by the Langmuir isotherm. When the coverage of the sites is plotted against the pressure (or concentration) of the adsorbing gas (or solute), it follows a rectangular hyperbolic path. However, when the adsorption is plotted in a specific manner, where the reciprocal of the coverage (or the fraction of the surface covered) is plotted against the reciprocal of the pressure (or concentration), a straight line is obtained. This linear plot is known as the Langmuir plot, and it is specifically designed to apply to a scenario where there is no interaction between adsorbed molecules and constant adsorption energy.