Mole Fraction Calculator for a Solute
Divide moles of solute by the total moles in the mixture, x = n_solute / (n_solute + n_solvent), for a dimensionless value from 0 to 1.
Fração molar
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Mole fraction (χ): composition of a solution
The mole fraction χᵢ of component i is just its moles divided by the total moles in the mixture: χᵢ = nᵢ / Σnⱼ. The value is dimensionless, sits somewhere between 0 and 1, and once you add up every component you get 1 (Σχᵢ = 1). Example: 1 mol of solute plus 9 mol of solvent gives χsolute = 0.1 and χsolvent = 0.9. Where molarity (mol/L) shifts with temperature and volume, the mole fraction doesn't budge, which is why it's the quantity you reach for in solution thermodynamics. Raoult's law: P = χsolvent · P° (vapor pressure of an ideal solution).
Applications
It underpins solution thermodynamics (Raoult and Henry laws) and fractional distillation, where separating petroleum or ethanol by boiling point hangs on χ. It shows up in gas mixtures, from medical oxygen therapy O₂/N₂ to breathable atmospheres for diving, and in the chemical engineering of separation columns and reactors. For ideal gases, the mole fraction matches the volume fraction (Avogadro's law).
FAQ
Mole fraction vs molarity? Molarity rides on volume, and volume changes with T. Mole fraction is baked into the composition itself, so it works well for thermodynamic calculations and colligative properties.
Can χ exceed 1? No. By definition χ ∈ [0, 1]. A value of 1 means the pure substance, and a value of 0 means it isn't there at all.
Mole percent? Take χ · 100%. So χ = 0.1 comes out as 10 mol%.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.