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Mole fraction Calculator

Calculate mole fraction of a component in a mixture.

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Mole Fraction

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Overview

Mole fraction is a dimensionless concentration unit that expresses the ratio of the number of moles of one component to the total number of moles of all components in a mixture. It is particularly useful in thermodynamics and physical chemistry because its value does not change with temperature or pressure variations.

Symbols

Variables

n_i = Moles of Component i, \sum n = Total Moles, x_i = Mole Fraction

Moles of Component i
Total Moles
Mole Fraction

Apply it well

When To Use

When to use: Use this equation when analyzing gas mixtures to determine partial pressures using Dalton's Law. It is also the standard for calculating colligative properties, such as vapor pressure lowering in Raoult's Law, where temperature-independent concentration units are required.

Why it matters: Mole fraction is essential in chemical engineering and respiratory therapy for calculating the specific concentration of gases in air or industrial pipelines. It ensures accurate stoichiometry in complex multi-phase systems where volume expansion might otherwise skew concentration measurements.

Avoid these traps

Common Mistakes

  • Using mass instead of moles.
  • Forgetting all mole fractions must sum to 1.

One free problem

Practice Problem

A gas mixture contains 2.5 moles of neon and 7.5 moles of argon. Calculate the mole fraction of neon in the mixture.

Moles of Component i2.5 mol
Total Moles10 mol

Solve for:

Hint: The total moles (nT) is the sum of neon and argon moles.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Atkins' Physical Chemistry
  2. IUPAC Gold Book: mole fraction
  3. Wikipedia: Mole fraction
  4. Atkins' Physical Chemistry, 11th Edition
  5. IUPAC Gold Book, 'mole fraction'
  6. Atkins' Physical Chemistry, 11th Edition, Peter Atkins, Julio de Paula, James Keeler
  7. Bird, Stewart, Lightfood - Transport Phenomena, 2nd Edition, R. Byron Bird, Warren E. Stewart, Edwin N. Lightfoot
  8. Edexcel A-Level Chemistry — Equilibria