Gás Real (Van der Waals simplif.)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
Van der Waals
About this calculator
The real gas calculator with the simplified Van der Waals equation allows estimating the molar volume of a real gas from pressure, temperature, and specific gas parameters (a and b). Unlike the ideal gas model, this equation accounts for attractive forces between molecules and the volume occupied by the molecules themselves, providing more realistic results under moderate temperature and pressure conditions.
The calculation is based on the Van der Waals equation: (P + a/V²)(V - b) = RT, where V is the molar volume. The simplified version used here iteratively solves for volume from the provided parameters. It is important to enter consistent values: pressure in atm, temperature in Kelvin, and parameters a (in L²·atm/mol²) and b (in L/mol) specific to each gas.
This tool is useful for chemical engineers, physicists, and students who need to size reactors, calculate gas properties in industrial processes, or check deviations from ideality. Avoid using it for gases at very high pressures (above 200 atm) or temperatures near the critical point, where the Van der Waals equation loses accuracy.
Frequently asked questions
What does the parameter 'a' mean in the Van der Waals equation?
The parameter 'a' represents the strength of attractive forces between gas molecules. The larger the value of 'a', the stronger the intermolecular attraction.
What is the correct unit for molar volume in the calculator?
Molar volume is provided in liters per mole (L/mol). Make sure parameters a and b are in compatible units (L²·atm/mol² and L/mol, respectively).
Does the calculator work for any real gas?
It works for gases whose parameters a and b are known. The Van der Waals equation is an approximation, being more accurate for non-polar gases under moderate conditions.
Why does the result differ from the ideal gas?
The ideal gas ignores molecular interactions and molecular volume. The Van der Waals equation corrects these factors, resulting in volumes generally smaller than ideal under moderate pressures.
Can I use this calculator for gas mixtures?
No. The calculator is designed for pure gases. For mixtures, specific mixing rules are needed, such as Van der Waals mixing rules.