M

Mole Fraction

x₁ = n₁ / Σnᵢ; Σxᵢ = 1; mol fraction of component i
Quick Reference
Formula / Notationx₁ = n₁ / Σnᵢ; Σxᵢ = 1; mol fraction of component i
Also Known AsMol fraction, molar fraction, x_i, mole fraction of component

What is Mole Fraction?

A dimensionless concentration unit defined as the ratio of the moles of one component to the total moles of all components in a mixture. Mole fractions range from 0 to 1 and always sum to 1 for all components. Used in Raoult's law and ideal gas mixture calculations.

Formula & Notation

x₁ = n₁ / Σnᵢ; Σxᵢ = 1; mol fraction of component i

Other Names / Synonyms: Mol fraction, molar fraction, x_i, mole fraction of component

Properties & Characteristics

Mole fraction (x_i) is the ratio of the number of moles of a component to the total number of moles of all components in a mixture: x_i = n_i / Σn_j. Mole fractions are dimensionless and sum to 1. They are used in Raoult's law (P_A = x_A × P°_A), Dalton's law of partial pressures (p_i = x_i × P_total), and thermodynamic equations. Mole fraction is particularly useful for gas mixtures and vapour-liquid equilibrium calculations.

Uses & Applications

Mole fractions are used in: vapour-liquid equilibrium calculations (Raoult's law, Henry's law), computing activities in non-ideal solutions, expressing gas mixture compositions (atmospheric O₂: x = 0.2095), calculating partial pressures, and in chemical equilibrium expressions for Kp in gas-phase reactions.

Safety Information

Mole fraction of toxic or flammable gases in a mixture determines their partial pressure and hence their potential to cause harm. Knowing mole fraction allows calculation of partial pressure of a toxic gas in a mixture — essential for comparing to TLV (threshold limit value) occupational exposure standards.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Mole Fraction
Formula x₁ = n₁ / Σnᵢ; Σxᵢ = 1; mol fraction of component i
Synonyms Mol fraction, molar fraction, x_i, mole fraction of component

Frequently Asked Questions

A dimensionless concentration unit defined as the ratio of the moles of one component to the total moles of all components in a mixture. Mole fractions range from 0 to 1 and always sum to 1 for all components. Used in Raoult's law and ideal gas mixture calculations.

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