Pressure Formula:
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Definition: This calculator computes the pressure of a real gas using the Clausius equation of state, which accounts for molecular size and intermolecular forces.
Purpose: It helps chemists and engineers accurately predict gas behavior under various conditions, especially near critical points.
The calculator uses the Clausius equation:
Where:
Explanation: The first term accounts for molecular volume exclusion, while the second term accounts for intermolecular attractive forces.
Details: The Clausius equation provides more accurate pressure predictions for real gases than the ideal gas law, especially at high pressures and low temperatures.
Tips: Enter all required parameters. Reduced temperature and volume are dimensionless ratios. Critical parameters and Clausius parameters are substance-specific.
Q1: What are typical values for Clausius parameters?
A: Parameters vary by substance. For example, for CO₂: a ≈ 0.3658 Pa·m⁶·K⁰·⁵/mol², b ≈ 4.28×10⁻⁵ m³/mol, c ≈ 4.34×10⁻⁵ m³/mol.
Q2: How do I obtain reduced temperature and volume?
A: Reduced temperature = T/Tc, Reduced volume = Vm/Vm,c, where T and Vm are actual temperature and molar volume.
Q3: Why does this equation work better than ideal gas law?
A: It accounts for finite molecular size (b parameter) and intermolecular forces (a parameter), which become significant for real gases.
Q4: What's the range of validity for this equation?
A: It works well for moderate pressures and temperatures, especially near the critical point.
Q5: How accurate is this calculator?
A: Accuracy depends on the precision of input parameters and how well the Clausius equation models your specific gas.