Surface Chemistry

Step 1: Understand Langmuir adsorption isotherm.
Langmuir isotherm assumes monolayer adsorption on a homogeneous surface.
All adsorption sites are identical and there is no interaction between adsorbed molecules.
Step 2: Mathematical expression.
The Langmuir isotherm equation is: where is fractional surface coverage, is adsorption equilibrium constant, and is pressure.
Step 3: Evaluation of options.
(A) Incorrect — Langmuir theory is limited to monolayer adsorption.
(B) and (C) Not defining statements of Langmuir isotherm.
(D) Correct — It gives the exact mathematical form of Langmuir isotherm.
Step 4: Conclusion.
Hence, option (D) is correct.