Mole Fraction Calculator
Calculate mole fraction of solute and solvent in a solution using moles. Free online chemistry calculator with step-by-step breakdowns and visual charts.
About This Calculator
The Mole Fraction Calculator computes the mole fraction of each component in a binary solution. Enter the moles of solute and solvent to instantly get the mole fractions, total moles, and a visual breakdown.
Mole fraction (X) is a dimensionless concentration unit defined as the ratio of moles of one component to the total moles of all components. It is widely used in physical chemistry for Raoult's law, Dalton's law of partial pressures, colligative properties, and phase equilibrium calculations.
About Mole Fraction
Mole fraction has several advantages: it is temperature-independent (unlike molarity), works for all types of mixtures (gases, liquids, solids), and the sum of all mole fractions always equals 1. For ideal solutions, the mole fraction is directly proportional to the partial vapor pressure.
The formula is: XA = nA / (nA + nB), where nA and nB are the number of moles of each component. The result is always between 0 and 1.
Frequently Asked Questions
What is mole fraction in chemistry?
Mole fraction (X) is the ratio of moles of one component to total moles in a mixture. It is a dimensionless quantity used in Raoult's law, partial pressure, and colligative properties calculations.
How do you calculate mole fraction?
Mole fraction (X_A) = moles of component A / total moles of all components. The sum of all mole fractions in a mixture always equals 1.
What is the difference between mole fraction and mass fraction?
Mole fraction uses moles (count of molecules), while mass fraction uses mass (grams). They differ when components have different molecular weights. Both are dimensionless but represent different ratios.
Can mole fraction be greater than 1?
No, mole fraction always ranges from 0 to 1 (0% to 100%). The sum of all mole fractions in a mixture always equals exactly 1.
How is mole fraction used in Raoult's law?
Raoult's law states that partial vapor pressure of a component equals its mole fraction times its pure vapor pressure. This is essential for distillation calculations and understanding ideal solutions.
What is the mole fraction of water in air?
The mole fraction of water vapor in air varies with humidity. At 25 degC and 50% relative humidity, water's mole fraction in air is approximately 0.016 (1.6%), which corresponds to the partial pressure of water vapor divided by atmospheric pressure.