Question

Langmuir isotherm

• A. Multilayer adsorption
• B. Very high temperature \( \theta \) vs \( P \) curve with intercept
• C. Very low temperature \( \theta \) vs \( P \) curve with slope
• D. Reciprocal form gives \( \theta = \dfrac{KP}{1+KP} \)

Hint:

Langmuir isotherm always represents monolayer adsorption and follows \( \theta = \dfrac{KP}{1+KP} \).

Answer 1

The Correct Option is D

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: \[ \theta = \frac{KP}{1+KP} \] where \( \theta \) is fractional surface coverage, \( K \) is adsorption equilibrium constant, and \( P \) 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.