Boiling Point
Normal boiling point: temperature when vapor pressure equals 1 atm. Governed by intermolecular forces and Clausius-Clapeyron. Lower P → lower BP.
Why This Chemistry Calculation Matters
Why: Boiling point depends on pressure. Normal BP at 1 atm. Distillation and high-altitude cooking rely on this relationship.
How: ln(P₂/P₁) = -(ΔHvap/R) × (1/T₂ - 1/T₁). Solve for T₂ or P₂. Temperatures in Kelvin.
- ●Water: 100°C at 1 atm; ~82°C at 0.5 atm.
- ●ΔHvap reflects intermolecular force strength.
- ●Lower pressure = lower boiling point.
- ●R = 8.314 J/(mol·K).
Boiling Point Examples
💧 Water at Sea Level
Standard atmospheric pressure
🏔️ Water at High Altitude
Lower pressure = lower boiling point
🍷 Ethanol Boiling Point
Ethanol at different pressures
📊 Pressure from Boiling Point
Calculate pressure at given temperature
⚗️ Methanol Boiling Point
Methanol vapor pressure calculation
🧪 Acetone Boiling Point
Acetone at reduced pressure
🔬 Benzene Boiling Point
Benzene vapor pressure
💨 Ammonia Boiling Point
Ammonia at different pressures
⚙️ Distillation Process
Reduced pressure distillation
🔥 High Pressure Boiling
Increased pressure increases BP
🧬 Toluene Boiling Point
Toluene vapor pressure
📝 Custom Substance
Calculate with custom values
Calculate Boiling Point
For educational and informational purposes only. Verify with a qualified professional.
🔬 Chemistry Facts
Normal BP: vapor pressure = 1 atm.
— IUPAC
ln(P₂/P₁) = -(ΔHvap/R)(1/T₂ - 1/T₁).
— NIST
Water ΔHvap ≈ 40.7 kJ/mol.
— CRC
Stronger IMFs → higher BP.
— Physical chem
📋 Key Takeaways
- • ln(P₂/P₁) = -(ΔHvap/R) × (1/T₂ - 1/T₁)
- • Lower pressure = lower boiling point
- • ΔHvap = enthalpy of vaporization (kJ/mol)
- • R = 8.314 J/(mol·K)
What is the Clausius-Clapeyron Equation?
Describes how vapor pressure depends on temperature. Fundamental for phase transitions and distillation.
ln(P₂/P₁) = -(ΔHvap/R) × (1/T₂ - 1/T₁)
How to Calculate
Given T₁, P₁, P₂ and ΔHvap: solve for T₂. Or given T₁, T₂, P₁: solve for P₂. Temperatures must be in Kelvin.
When to Use
Distillation
Design reduced-pressure distillation.
High-Altitude Cooking
Understand boiling at different pressures.
Formulas
ln(P₂/P₁) = -(ΔHvap/R) × (1/T₂ - 1/T₁)
Rearrange for T₂ or P₂ as needed.
Common Substances
| Substance | Normal BP (°C) | ΔHvap (kJ/mol) |
|---|---|---|
| Water | 100 | 40.7 |
| Ethanol | 78.37 | 38.6 |
| Methanol | 64.7 | 35.2 |
| Acetone | 56.2 | 29.1 |
| Benzene | 80.1 | 30.8 |
| Toluene | 110.6 | 33.2 |
| Chloroform | 61.2 | 29.2 |
| Diethyl ether | 34.6 | 26.5 |
| Ammonia | -33.34 | 23.3 |
| Carbon tetrachloride | 76.7 | 30 |
Practical Examples
Water at 0.5 atm boils at ~82°C. Ethanol at 0.8 atm boils at ~72°C.
📚 Official Data Sources
⚠️ Disclaimer: Consult NIST and CRC for precision work.
Related Calculators
Vapor Pressure Calculator
Calculate vapor pressure at different temperatures using Clausius-Clapeyron equation and Antoine equation. Supports common substances and custom calculations.
ChemistryClausius-Clapeyron Calculator
Calculate vapor pressure at different temperatures, enthalpy of vaporization, and boiling points using the Clausius-Clapeyron equation for phase equilibrium...
ChemistryEnthalpy of Vaporization Calculator
Calculate enthalpy of vaporization from Clausius-Clapeyron data, heat required for phase transitions (q = nΔHvap), and Trouton's Rule estimation for chemical thermodynamics calculations.
ChemistryBoiling Point at Altitude Calculator
Calculate boiling point based on altitude. Understand how atmospheric pressure affects boiling temperatures at different elevations.
ChemistryBoiling Point Elevation Calculator
Calculate boiling point elevation for solutions using colligative properties. Determine how solutes affect boiling point.
ChemistryClausius-Mossotti Calculator
Calculate dielectric constant from polarizability, molecular polarizability from dielectric measurements, and molar refractivity using the Clausius-Mossotti...
Chemistry