Total Volume of Gas Adsorbed at Equilibrium by BET Equation Calculator

BET Equation Formula:

\[ V_{total} = \frac{V_{mono} \times C \times \left(\frac{P_v}{P_0}\right)}{\left(P_v - \left(\frac{P_v}{P_0}\right)\right) \times \left(1 + \left(C \times \left(\frac{P_v}{P_0}\right)\right)\right) - \left(\frac{P_v}{P_0}\right)} \]

Monolayer Volume of Gas (V_mono):

m³

Adsorbent Constant (C):

Vapour Pressure (P_v):

Saturated Vapor Pressure (P₀):

Total Equilibrium Volume of Gas (V_total): m³

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the BET Equation Calculator?

Definition: This calculator determines the total volume of gas adsorbed at equilibrium using the Brunauer-Emmett-Teller (BET) equation.

Purpose: It's used in surface chemistry to measure the specific surface area of materials by gas adsorption.

2. How Does the BET Equation Work?

The calculator uses the BET equation:

Where:

\( V_{total} \) — Total equilibrium volume of gas adsorbed (m³)
\( V_{mono} \) — Monolayer volume of gas (m³)
\( C \) — Adsorbent constant (dimensionless)
\( P_v \) — Vapour pressure (Pa)
\( P_0 \) — Saturated vapor pressure (Pa)

Explanation: The equation describes physical adsorption of gas molecules on a solid surface and extends the Langmuir isotherm to multilayer adsorption.

3. Importance of BET Equation

Details: The BET theory is the most widely used method for determining the surface area of porous materials and powders.

4. Using the Calculator

Tips:

Enter all values in the specified units
Vapour pressure (P_v) must be less than or equal to saturated vapor pressure (P₀)
All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is the monolayer volume (V_mono)?
A: It's the volume of gas required to form a single molecular layer on the adsorbent surface.

Q2: What does the adsorbent constant (C) represent?
A: C is related to the energy of adsorption in the first adsorbed layer and varies with the adsorbent-adsorbate system.

Q3: Why must P_v ≤ P₀?
A: The relative pressure (P_v/P₀) must be between 0 and 1 for the BET theory to be valid.

Q4: What is a typical range for the C constant?
A: C values typically range from 50 to 300 for nitrogen adsorption at 77K.

Q5: What materials can be analyzed with BET theory?
A: The BET method is suitable for most porous and powder materials including catalysts, zeolites, activated carbons, and metal-organic frameworks.