Calculate Enthalpy Of Vaporization

Clausius-Clapeyron Equation:

\[ \Delta H_v = R \times \frac{T_1 \times T_2}{T_2 - T_1} \times \ln\left(\frac{P_2}{P_1}\right) \]

Gas Constant (R):

J/mol·K

Temperature 1 (T₁):

Temperature 2 (T₂):

Pressure 1 (P₁):

Pressure 2 (P₂):

Enthalpy Of Vaporization (ΔH_v):

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1. What is the Clausius-Clapeyron Equation?

The Clausius-Clapeyron equation describes the relationship between vapor pressure and temperature for a substance. It's used to calculate the enthalpy of vaporization (ΔH_v), which is the energy required to convert a liquid to a vapor at constant temperature and pressure.

2. How Does the Calculator Work?

The calculator uses the Clausius-Clapeyron equation:

\[ \Delta H_v = R \times \frac{T_1 \times T_2}{T_2 - T_1} \times \ln\left(\frac{P_2}{P_1}\right) \]

Where:

\( R \) — Gas constant (8.314 J/mol·K)
\( T_1, T_2 \) — Temperatures in Kelvin
\( P_1, P_2 \) — Vapor pressures at T₁ and T₂ respectively (Pa)
\( \ln \) — Natural logarithm

Explanation: The equation relates the change in vapor pressure with temperature to the enthalpy of vaporization, assuming ideal gas behavior and constant ΔH_v over the temperature range.

3. Importance of Enthalpy of Vaporization

Details: Enthalpy of vaporization is a crucial thermodynamic property that indicates the strength of intermolecular forces in a liquid. It's important in chemical engineering, material science, and environmental studies for designing separation processes, predicting phase behavior, and understanding climate systems.

4. Using the Calculator

Tips: Enter the gas constant (typically 8.314 J/mol·K), two different temperatures in Kelvin, and the corresponding vapor pressures in Pascals. Ensure T₂ ≠ T₁ and all values are positive.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for enthalpy of vaporization?
A: For water at 100°C, it's about 40.7 kJ/mol. Values range from 5-50 kJ/mol for most common liquids.

Q2: Why must temperatures be in Kelvin?
A: The equation requires absolute temperature because it involves ratios and logarithms of temperatures.

Q3: What are the limitations of this equation?
A: It assumes constant enthalpy of vaporization and ideal gas behavior, which may not hold over large temperature ranges.

Q4: Can I use different pressure units?
A: Yes, but both pressures must be in the same units, and the gas constant may need adjustment if using different units.

Q5: How accurate is this calculation?
A: It provides a good estimate for many substances, but for precise work, experimental measurement or more sophisticated equations may be needed.