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Chemistry

Mole Fraction

Express a component’s share of the total amount of substance.

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Source & review

Difficulty

Beginner

Read time

3 min

Prerequisites

Basic algebra and molar quantities

Review statusNeeds review

Source

OpenStax, Chemistry 2e, §9.3

Adapted from Teng-Jui Lin’s CHEM 145 equation sheet. The linked textbook reference was used to check the equation and its physical context. Pending editorial review.

Adapted from Teng-Jui Lin, Equation Sheets, under CC BY 4.0.

FormuLab adapted notation and chemical symbols, added variable meanings, units, applicability conditions, and an original worked example.

Definition
Understanding the core concept

A mole fraction compares the moles of one component with the total moles in a mixture. It is dimensionless, lies between zero and one, and the component fractions sum to one.

Variables & Units
Understanding each component
SymbolMeaningUnits
Mole fraction of component i
Amount of component i
Total amount of all mixture components
Real-World Applications
Where this formula is used in practice

Mixture composition

Report gas or liquid composition on a molar basis.

Gas blending

Convert a component amount into a fraction for partial-pressure calculations.

Worked Example
Step-by-step calculation with real numbers

Problem

A mixture contains 3.00 mol of nitrogen and 7.00 mol of another gas. Find the nitrogen mole fraction.

Given

Solution

1
2
3

Final Answer

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