Calculate Boiling Point From Vapor Pressure

Boiling Point Equation:

\[ T_b = \frac{1}{\frac{1}{T_0} - \frac{R}{\Delta H_{vap}} \ln \left( \frac{P}{P_0} \right)} \]

Reference Temperature (T₀):

Enthalpy of Vaporization (ΔH_vap):

J/mol

Vapor Pressure (P):

Reference Pressure (P₀):

Boiling Point (T_b):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Boiling Point Equation?

The boiling point equation calculates the boiling temperature of a substance based on vapor pressure data using the Clausius-Clapeyron relation. It provides a thermodynamic approach to determine how boiling point changes with pressure.

2. How Does the Calculator Work?

The calculator uses the boiling point equation:

\[ T_b = \frac{1}{\frac{1}{T_0} - \frac{R}{\Delta H_{vap}} \ln \left( \frac{P}{P_0} \right)} \]

Where:

\( T_b \) — Boiling point (K)
\( T_0 \) — Reference temperature (K)
\( R \) — Gas constant (8.314 J/mol·K)
\( \Delta H_{vap} \) — Enthalpy of vaporization (J/mol)
\( P \) — Vapor pressure (Pa)
\( P_0 \) — Reference pressure (Pa)

Explanation: The equation derives from the Clausius-Clapeyron relation and describes how boiling temperature varies with pressure for a given substance.

3. Importance of Boiling Point Calculation

Details: Accurate boiling point calculation is crucial for chemical process design, distillation operations, pharmaceutical manufacturing, and understanding substance behavior under different pressure conditions.

4. Using the Calculator

Tips: Enter reference temperature in Kelvin, enthalpy of vaporization in J/mol, vapor pressure in Pascal, and reference pressure in Pascal. All values must be positive and non-zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the Clausius-Clapeyron equation?
A: The Clausius-Clapeyron equation describes the relationship between vapor pressure and temperature for a pure substance, forming the basis for this boiling point calculation.

Q2: Why use Kelvin for temperature?
A: Kelvin is an absolute temperature scale required for thermodynamic calculations where zero represents absolute zero, making it essential for accurate scientific computations.

Q3: What are typical values for enthalpy of vaporization?
A: Enthalpy of vaporization varies by substance. Water has ΔH_vap ≈ 40.65 kJ/mol, while organic solvents typically range from 20-50 kJ/mol at their boiling points.

Q4: How accurate is this calculation?
A: The calculation assumes constant enthalpy of vaporization and ideal gas behavior, which is generally valid for moderate pressure ranges but may require corrections for extreme conditions.

Q5: Can this be used for mixed substances?
A: This equation is designed for pure substances. For mixtures, additional factors like composition and activity coefficients must be considered.