Clausius-Clapeyron Equation Calculator

Calculate the pressure ratio between two states while keeping full control over temperatures and enthalpy of vaporization values.

Input values

How to Use This Calculator

The Clausius-Clapeyron Equation Calculator is designed for advanced chemistry students and professionals who need to calculate phase transition properties. This tool helps solve problems related to phase changes in substances.

Enter the pair of temperatures in Kelvin and the corresponding enthalpy of vaporization in joules per mole. Click Calculate to derive the pressure ratio between the two states. Reset returns the inputs to the example values, and the interface enforces positive numeric entries.

Methodology

All calculations are based strictly on the Clausius-Clapeyron equation as described in standard chemistry textbooks. The formula is evaluated in logarithmic form and then exponentiated to obtain the pressure ratio. Ensure data accuracy by consulting reliable scientific sources and keeping units consistent.

Glossary of terms

  • T1: Initial temperature in Kelvin.
  • T2: Final temperature in Kelvin.
  • ΔHvap: Enthalpy of vaporization in joules per mole.
  • P2/P1: Pressure ratio between final and initial states.

How it works: a step-by-step example

Consider a substance with an initial temperature (T1) of 300 K and a final temperature (T2) of 350 K, with an enthalpy of vaporization (ΔHvap) of 40,000 J/mol. Using the Clausius-Clapeyron equation, the pressure ratio P2/P1 can be calculated by plugging these values into the logarithmic form, then exponentiating the result.

Frequently asked questions

What is the Clausius-Clapeyron equation used for?

It describes phase transitions between two phases of matter, such as liquid to gas.

Why are temperatures required in Kelvin?

Kelvin is the absolute temperature scale used in thermodynamic equations to ensure proportionality and accuracy.

How does ΔHvap affect the calculation?

The enthalpy of vaporization directly influences the pressure change; higher values indicate more energy required for phase change.

Can this calculator be used for all substances?

Yes, provided you have the necessary input values like temperature and enthalpy of vaporization.

Where can I find reliable ΔHvap values?

Consult scientific literature or databases for accurate enthalpy values specific to each substance.

Formulas

Clausius-Clapeyron:

ln(P2/P1) = (ΔHvap / R) × (1/T1 - 1/T2)

R is the universal gas constant, equal to 8.314 J/mol·K.

  • P2/P1: Pressure ratio after exponentiation.
  • ΔHvap: Enthalpy of vaporization in joules per mole.
  • T1, T2: Temperatures in Kelvin.
Citations
Changelog

Version: 0.1.0-draft · Last code update: 2026-01-19

  • Initial Clausius-Clapeyron calculator with validated inputs and deterministic formatting.
  • Documented methodology, glossary, and illustrative FAQ to support advanced thermodynamics work.
  • Structured metadata mirrors CalcDomain's canonical layout for consistency.
Verified by Ugo Candido Last Updated: 2026-01-19 Version 0.1.0-draft
Version 1.5.0