Concentration Calculator (ppm, Molality, Mole Fraction)
Convert between ppm, ppb, molality and mole fraction. Enter masses and moles and get each concentration with the formula and the working.
What this calculator does
Calculate parts per million and billion, molality and mole fraction from the amounts of solute and solvent, with the substitution shown.
When you need it
Different fields use different concentration units: ppm for water quality, molality for colligative properties, mole fraction for gas and vapor calculations. Converting between them is a routine task.
Formulas
- ppm = (mass of solute ÷ mass of solution) × 10⁶
- molality m = moles of solute ÷ kilograms of solvent
- mole fraction χA = nA ÷ (nA + nB)
How to use it
- Choose ppm and ppb, molality or mole fraction.
- Enter the masses or moles of solute and solvent.
- Read the concentration and the substitution step.
Worked example
What is the molality of a solution with 5.85 g of NaCl (M = 58.44 g/mol) in 500 g of water?
- n(NaCl) = 5.85 ÷ 58.44 = 0.100 mol
- Solvent = 500 g = 0.500 kg
- m = 0.100 mol ÷ 0.500 kg = 0.200 mol/kg
Answer
The solution is 0.200 mol/kg.
Common mistakes
- Dividing by the mass of the solution instead of the solvent for molality.
- Using grams instead of kilograms for the solvent.
- Confusing molality (mol/kg solvent) with molarity (mol/L solution).
Related tools
Frequently asked questions
What is the difference between molarity and molality?
Molarity is moles per liter of solution; molality is moles per kilogram of solvent. Molality does not change with temperature.
What does ppm mean?
Parts per million: 1 ppm is 1 mg of solute per kg of solution, about 1 mg per liter for dilute water solutions.
What is mole fraction?
The moles of one component divided by the total moles of all components. The mole fractions of a solution add up to 1.