Formula Used:
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Definition: This calculator determines the change in enthalpy during a phase transition using pressure and temperature measurements.
Purpose: It's used in thermodynamics to calculate the heat content change during processes like vaporization or sublimation.
The calculator uses the integrated form of the Clausius-Clapeyron equation:
Where:
Explanation: The natural log of the pressure ratio is multiplied by the gas constant and divided by the difference in reciprocal temperatures.
Details: Enthalpy change calculations are crucial for designing heat exchangers, refrigeration systems, and understanding phase transitions.
Tips: Enter initial and final pressures in Pascals, and temperatures in Kelvin. All values must be positive numbers.
Q1: What units should I use for input?
A: Pressure must be in Pascals (Pa) and temperature in Kelvin (K) for accurate results.
Q2: When is this equation valid?
A: For phase transitions where the vapor phase behaves as an ideal gas and the molar volume of liquid is negligible.
Q3: What does a negative enthalpy change mean?
A: A negative value indicates an exothermic process (heat is released).
Q4: Can I use this for solid-liquid transitions?
A: No, this form is primarily for vapor-liquid or vapor-solid transitions.
Q5: Why use natural logarithm in the formula?
A: The ln function comes from integrating the differential form of the Clausius-Clapeyron equation.