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Normal Boiling Point Equation:
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The normal boiling point equation \( T_b = \frac{\Delta H_{vap}}{\Delta S_{vap}} \) calculates the boiling temperature at 1 atm pressure from thermodynamic properties. It assumes that at the boiling point, the liquid and vapor phases are in equilibrium.
The calculator uses the boiling point equation:
Where:
Explanation: For many liquids, the entropy of vaporization is approximately 88 J/mol·K (Trouton's rule), making this a useful estimation method when experimental data is limited.
Details: Accurate boiling point prediction is essential for chemical process design, separation techniques, safety considerations, and understanding substance behavior under different temperature conditions.
Tips: Enter heat of vaporization in J/mol and entropy of vaporization in J/mol·K. The default entropy value of 88 J/mol·K follows Trouton's rule for many common liquids.
Q1: What is Trouton's rule?
A: Trouton's rule states that the entropy of vaporization is approximately 88 J/mol·K for many non-associated liquids at their normal boiling points.
Q2: When does this equation not apply well?
A: The equation may be less accurate for associated liquids (like water with hydrogen bonding) or polar substances where Trouton's rule deviations occur.
Q3: Can I use this for mixtures?
A: This equation is primarily for pure substances. Mixtures have different boiling behavior due to composition changes during vaporization.
Q4: How accurate is this estimation method?
A: For many simple liquids, the estimation is within 5-10% of experimental values when using the standard 88 J/mol·K entropy value.
Q5: What units should I use?
A: Use consistent SI units: J/mol for enthalpy and J/mol·K for entropy to get boiling point in Kelvin.