 Equilibrium constant (K eq)
Partial pressure (P)
Pa
Surface fraction (θ)
Surface percent
%

# Langmuir Isotherm Calculator

By Łucja Zaborowska

The Langmuir Isotherm calculator is an easy-to-use tool for computing the fraction or percent of the adsorbent surface covered by an adsorbate using the Langmuir model.

Our Langmuir Isotherm calculator allows you to use either the partial pressure or the molarity of the substance, depending whether you're calculating the isotherm for a gas or for a liquid.

## What is Langmuir adsorption isotherm?

Firstly, we'd like to remind you of a few basic definitions:

• Adsorption - is a process of adhesion that connects molecules, atoms, or ions to a surface (or a phase boundary).

• In this process, the adsorbate creates a thin layer on the surface of the adsorbent.

• Chemisorption - a type of adsorption that creates strong chemical bonds between the adsorbate and the adsorbent.

• Isotherm - is a function that describes the change in the amount of adhered substance, depending on the substance's partial pressure or concentration. The reaction must take place in isothermal conditions (that is, with constant temperature). 🌡️

Coming back to the Langmuir theory:

The Langmuir isotherm assumes that the adsorbate can only create a monolayer of particles on the adsorbent's surface. These particles interact only with the adsorbent (vertical interactions) and do not interact with each other (horizontal interactions).

Langmuir isotherm is based on these assumptions:

• The adsorbate particles behave as an ideal gas;
• The energy of the surface is homogeneous (identical and flat in all the places); and
• The adsorbate particles can not create multi-layers.

Read more on the characteristics of this adhesion process in the section below 📄

## How to calculate Langmuir isotherm?

We understand that even the best of Langmuir isotherm calculators can not replace actual knowledge. In this section, you can discover the formula we use in every detail.

Our tool uses the following Langmuir isotherm equation:

`θ = (Keq * P) / (1 + (Keq * P))`

Where:

• θ - fraction of the surface covered by adsorbate;
• Keq - equilibrium constant of adsorbtion; and
• P - partial pressure of the gas, or the molar concentration of the liquid.

In order to receive the percentage of the surface covered by the adsorbate, use the equation below:

`θpercent = θfraction * 100 `

## How to plot the Langmuir adsorption isotherm?

This is one of the most common questions regarding the adsorption isotherm; in order to answer it, we first need to understand the rules of Langmuir adsorption model.