Question

The Langmuir adsorption isotherm is deduced by using the assumption :

• A. the adsorption takes place in multilayers
• B. the adsorption sites are equivalent in their ability to adsorb the particles
• C. the heat of adsorption varies with coverage
• D. the adsorbed molecules interact with each other

Answer 1

The Correct Option is B

The Langmuir adsorption isotherm is a model that describes the adsorption of molecules onto a surface. It is based on certain key assumptions, and understanding these assumptions is crucial in determining the correct answer to the given question. Let's examine each option to identify the correct assumption:

1. The adsorption takes place in multilayers:
   • This option is incorrect. The Langmuir model assumes monolayer adsorption, meaning that adsorption occurs in a single layer on the surface and not in multiple layers.
2. The adsorption sites are equivalent in their ability to adsorb the particles:
   • This option is correct. The Langmuir model assumes that all adsorption sites on the surface are equivalent in their energy and ability to adsorb particles. This simplifies the model and allows for the derivation of the Langmuir isotherm equation.
3. The heat of adsorption varies with coverage:
   • This option is incorrect. The Langmuir model assumes that the heat of adsorption remains constant and does not vary with surface coverage. This assumption is necessary to maintain a uniform energy landscape across all sites.
4. The adsorbed molecules interact with each other:
   • This option is incorrect. The Langmuir model assumes that there is no interaction between adsorbed molecules, which means the adsorption of one particle doesn't affect the adsorption of another.

In conclusion, the correct assumption required for the Langmuir adsorption isotherm is that the adsorption sites are equivalent in their ability to adsorb particles, making the second option the correct answer.