Pressure Formula:
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Definition: The Modified Berthelot equation is a thermodynamic equation of state that relates pressure, temperature, molar volume, reduced pressure, and reduced temperature for real gases.
Purpose: It provides a more accurate calculation of pressure for real gases compared to the ideal gas law, especially at moderate pressures and temperatures.
The calculator uses the formula:
Where:
Explanation: The equation modifies the ideal gas law with correction terms that account for molecular interactions and non-ideal behavior.
Details: This equation provides better accuracy than the ideal gas law for real gases under many conditions, while remaining relatively simple compared to more complex equations of state.
Tips: Enter the temperature in Kelvin, molar volume in m³/mol, reduced pressure (dimensionless), and reduced temperature (dimensionless). All values must be positive.
Q1: What is reduced pressure and temperature?
A: Reduced pressure (Pr) is the ratio of actual pressure to critical pressure. Reduced temperature (Tr) is the ratio of actual temperature to critical temperature.
Q2: When is this equation most accurate?
A: The Modified Berthelot equation works well for moderate pressures (not too high) and temperatures above the critical temperature.
Q3: What are typical values for reduced parameters?
A: Reduced parameters typically range from 0 to 1 for subcritical conditions, but can be greater than 1 for supercritical conditions.
Q4: How do I find critical properties?
A: Critical properties (temperature and pressure) are tabulated for many substances in thermodynamic reference tables.
Q5: What are the limitations of this equation?
A: It becomes less accurate at very high pressures or near the critical point where more complex equations of state are needed.