Mole fraction calculator explained
Mole fraction () gives the ratio of moles of component to the total moles in a mixture. Because it is dimensionless, it is ideal for Raoult's law, phase-equilibrium simulations, and reporting feed compositions. This calculator sums the supplied solute and solvent moles to compute {mfraction}, mole percent {mpercentage}, and an optional molality {molality}.
Use it to convert from laboratory amounts to inputs for thermodynamic models or to verify that component fractions sum to 1.000.
How the conversion works
Given solute moles and total moles :
If you know molar mass of the solvent () and mole fraction, you can compute molality () via
The calculator automates these steps.
Units and conversions
| Quantity | Units | Notes |
|---|---|---|
| Solute (moles) | mol | Enter the amount of the component of interest. |
| Solvent (moles) | mol | Convert masses to moles before entering. |
| Mole fraction | dimensionless | Between 0 and 1. |
| Mole percent | % | 100 . |
| Molality | mol/kg solvent | Requires solvent molar mass if starting from mole fractions. |
Worked examples
- Ethanol-water mixture
, .
Mole percent = 29.4%; water mole fraction = 0.706.
- Mass-based input
10.0 g NaCl ( g/mol) dissolved in 90.0 g water ( g/mol).
The calculator also reports mole percent (3.3%) and molality (3.4 mol/kg).
Tips and pitfalls
- Mole fractions should sum to exactly 1.000 within rounding; if not, recheck your mole conversions.
- Use mole fractions (not weight fractions) when applying Raoult's or Dalton's laws because vapor-liquid equilibrium depends on mole ratios.
- For gas mixtures, compute moles from partial pressures using the ideal gas law before entering values.
- When converting between molality and mole fraction, remember molality uses kilograms of solvent, not solution.