Calculate Boiling Point At Different 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

Pressure (P):

Reference Pressure (P₀):

Boiling Point (T_b):

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1. What is the Boiling Point Equation?

The boiling point equation calculates the boiling temperature of a substance at different pressures using the Clausius-Clapeyron relation. It accounts for how pressure changes affect the boiling point of liquids.

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 at pressure P (K)
\( T_0 \) — Reference boiling point at pressure P₀ (K)
\( R \) — Gas constant (8.314 J/mol·K)
\( \Delta H_{vap} \) — Enthalpy of vaporization (J/mol)
\( P \) — Pressure at which boiling point is calculated (Pa)
\( P_0 \) — Reference pressure (Pa)

Explanation: The equation shows the inverse relationship between pressure and boiling point - as pressure decreases, boiling point decreases, and vice versa.

3. Importance of Boiling Point Calculation

Details: Accurate boiling point calculation is crucial for chemical processes, distillation, food processing, and understanding how altitude affects cooking times.

4. Using the Calculator

Tips: Enter all values in appropriate units. Ensure reference temperature and pressure correspond to known boiling point data. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why does boiling point change with pressure?
A: Boiling occurs when vapor pressure equals atmospheric pressure. Lower pressure means less energy needed for molecules to escape, lowering boiling point.

Q2: What are typical enthalpy of vaporization values?
A: Water: ~40.7 kJ/mol, Ethanol: ~38.6 kJ/mol, Acetone: ~31.0 kJ/mol. Values vary with temperature.

Q3: How does altitude affect boiling point?
A: At higher altitudes, atmospheric pressure is lower, causing water to boil at lower temperatures (about 1°C lower per 300m elevation).

Q4: Are there limitations to this equation?
A: The equation assumes constant enthalpy of vaporization and ideal gas behavior, which may not hold over large temperature ranges.

Q5: Can this be used for all liquids?
A: The equation works best for simple liquids without strong molecular interactions. Complex molecules may require more sophisticated models.