Vapor Pressure Calculator


Calculation Details:

What is Vapor Pressure?

Vapor pressure is a critical concept in engineering, particularly in the fields of thermodynamics and material science. It refers to the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The vapor pressure of a substance indicates its evaporation rate; higher vapor pressure means the substance evaporates more readily. This concept is essential for understanding phenomena like boiling, sublimation, and the behavior of refrigerants.

Vapor pressure varies with temperature. As the temperature increases, the kinetic energy of the molecules in the liquid or solid form increases, leading to a higher rate of evaporation and consequently a higher vapor pressure. This relationship between temperature and vapor pressure is not only fundamental in predicting the behavior of liquids in various conditions but also crucial in applications like distillation and in designing cooling systems.

Vapor Pressure Calculator

\( \frac{dP}{dT} = \frac{L}{T(V_{vapor} – V_{liquid})} \)


  • dP/dT – Rate of change of pressure with temperature,
  • L – Latent heat of vaporization,
  • T – Absolute temperature,
  • Vvapor – Specific volume of the vapor,
  • Vliquid – Specific volume of the liquid.

Vapor Pressure Calculator uses the Clausius-Clapeyron Equation to calculate the vapor pressure at a given temperature. This tool is essential for scientists and engineers working in fields like chemical engineering, environmental science, and material science, providing a critical understanding of the behavior of liquids and gases under various conditions.

Real World Applications

Understanding vapor pressure has practical applications in various engineering domains:

  1. Chemical Engineering: In distillation processes, knowing the vapor pressures of components helps in separating mixtures effectively.
  2. Mechanical Engineering: In refrigeration and air conditioning systems, the selection of refrigerants depends on their vapor pressures at different temperatures.
  3. Environmental Engineering: Vapor pressure is a key factor in studying the evaporation of pollutants in the atmosphere.
  4. Pharmaceuticals: The stability and storage conditions of many pharmaceuticals are determined by their vapor pressures.

These applications highlight the importance of vapor pressure in not only theoretical studies but also in practical, real-world problem-solving.

Frequently Asked Questions

  1. What Factors Affect Vapor Pressure?
    • Temperature: Vapor pressure increases with temperature.
    • Intermolecular Forces: Substances with weaker intermolecular forces have higher vapor pressures.
  2. How is Vapor Pressure Measured?
    • Vapor pressure can be measured using methods like the isoteniscope and manometric measurements.
  3. Why is Vapor Pressure Important in Distillation?
    • In distillation, the separation of components is based on their differing vapor pressures.


Vapor pressure is a fundamental concept in engineering, bridging the gap between theoretical studies and practical applications. Its understanding is crucial in fields ranging from chemical to environmental engineering. The Clausius-Clapeyron Equation offers a mathematical framework to relate vapor pressure with temperature, enhancing our ability to predict and manipulate the behavior of substances under varying conditions. As technology advances, the principles of vapor pressure will continue to play a vital role in new and innovative engineering solutions.