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Total vapour pressure Calculator

Total vapour pressure is the sum of partial pressures.

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Total Pressure

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Overview

Total vapor pressure represents the cumulative force per unit area exerted by all volatile components in a gas phase at equilibrium with their liquid counterparts. In physical chemistry, this is fundamentally described by Dalton’s Law of Partial Pressures, which states that the total pressure is the sum of the pressures each component would exert if it occupied the volume alone.

Symbols

Variables

P_1 = Partial Pressure 1, P_2 = Partial Pressure 2, P_{total} = Total Pressure

Partial Pressure 1
Partial Pressure 2
Total Pressure

Apply it well

When To Use

When to use: Use this formula when analyzing a mixture of non-reacting vapors or gases in a closed system to find the combined pressure. It is particularly relevant when working with Raoult's Law calculations for multi-component liquid solutions where each component contributes to the headspace pressure.

Why it matters: Understanding total vapor pressure is vital for the design of distillation columns in chemical engineering and for predicting the boiling points of mixtures. It also plays a key role in environmental science for determining the concentration of pollutants in the atmosphere above contaminated water sources.

Avoid these traps

Common Mistakes

  • Forgetting to include all volatile components.
  • Confusing with Raoult's law.

One free problem

Practice Problem

A container holds a mixture of two volatile liquids. At a specific temperature, the partial pressure of component 1 is 145 mmHg and the partial pressure of component 2 is 210 mmHg. Calculate the total vapour pressure of the system.

Partial Pressure 1145 kPa
Partial Pressure 2210 kPa

Solve for:

Hint: The total pressure is simply the sum of the individual partial pressures.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Atkins, P. W., & de Paula, J. (2014). Atkins' Physical Chemistry (10th ed.). Oxford University Press.
  2. Halliday, D., Resnick, R., & Walker, J. (2014). Fundamentals of Physics (10th ed.). Wiley.
  3. Wikipedia: Dalton's law
  4. IUPAC Gold Book
  5. Atkins' Physical Chemistry
  6. NIST Chemistry WebBook
  7. Peter Atkins, Julio de Paula, James Keeler. Atkins' Physical Chemistry. 11th ed. Oxford University Press, 2018.
  8. IUPAC Gold Book. 'Ideal gas'. DOI: 10.1351/goldbook.I02932.