---
title: "Mole Fraction — AP Chemistry Definition & Exam Guide"
description: "Mole fraction (X) is moles of one component divided by total moles in a mixture. It powers partial pressure math (P_A = P_total × X_A) in AP Chem Unit 3."
canonical: "https://fiveable.me/ap-chem/key-terms/mole-fraction"
type: "key-term"
subject: "AP Chemistry"
---

# Mole Fraction — AP Chemistry Definition & Exam Guide

## Definition

Mole fraction is a way of expressing concentrations for mixtures of liquids or solids. It represents the number of moles of one component divided by total moles in solution or mixture.

## Related Study Guides

- [9.5 Free Energy and Equilibrium](/ap-chem/unit-9/free-energy-equilibrium/study-guide/ConxkA0PUZM7vwf8nPNr)
- [3.4 Ideal Gas Law](/ap-chem/unit-3/ideal-gas-law/study-guide/XINb2AUU6e3c1rGlhBXg)

## Review

### Related Terms

- [Molarity](/ap-chem/key-terms/molarity): A concentration term used often in chemistry which measures moles solute per liter solution.
- [Molality](/ap-chem/key-terms/molality): Another concentration term which measures moles solute per kilogram solvent.
- [Mole](/ap-chem/key-terms/mole): A unit of measurement in chemistry that quantifies the amount of a substance. It is equivalent to Avogadro's number (6.022 x 10^23) of particles (atoms, molecules, ions etc.).