What is the Concentration Converter?
Chemists express solution composition in several units. Molarity (mol/L of solution) is common in volumetric work. Molality (mol/kg of solvent) is preferred when temperature changes matter. Mass percent and ppm appear in analytical and environmental contexts. Converting among them requires the solute’s molar mass and, for most conversions, the solution density.
The Concentration Converter takes one known concentration plus molar mass (from a formula or a typed value) and density, then reports molarity, g/L, g/mL, mg/mL, mass percent, ppm, and molality on a 1.00 L solution basis. Density-aware examples (saline, glucose, ethanol) help connect classroom molarity problems to everyday g↔mL style conversions.
For dilute aqueous solutions, density ≈ 1.00 g/mL is a standard classroom approximation. Concentrated acids, bases, and syrups need a measured or tabulated density or the conversion will be off.
- Molarity M = moles solute / liters solution
- Molality m = moles solute / kilograms solvent
- Mass % and ppm need density to relate mass of solute to volume of solution
Mathematical / chemical formulas
For 1.00 L of solution with density ρ (g/mL) and solute molar mass M (g/mol):
Mass of solution ≈ 1000ρ grams
Mass of solute (g) = (molarity) × M
Mass % = (mass solute / mass solution) × 100%
ppm (mass) = (mass solute / mass solution) × 10⁶
Molality = moles solute / kg solvent
kg solvent = (mass solution − mass solute) / 1000- ppm here is mass ppm (mg/kg). For very dilute water solutions this is nearly mg/L.
- If solute mass exceeds solution mass, the inputs are physically inconsistent.
Step-by-step example: 0.100 M NaCl with density 1.00 g/mL
Convert 0.100 M aqueous NaCl (M ≈ 58.44 g/mol, ρ = 1.00 g/mL) into g/L, mass percent, ppm, and molality.
- g/L = 0.100 × 58.44 = 5.844 g/L.
- In 1.00 L, solution mass ≈ 1000 g; solute = 5.844 g.
- Mass % ≈ (5.844 / 1000) × 100 = 0.584%.
- ppm ≈ 5844.
- kg solvent ≈ 0.994 kg; molality ≈ 0.100 / 0.994 ≈ 0.101 mol/kg.
Enter NaCl, density 1.00, molarity 0.100 in the Concentration Converter and compare the table of results.
Frequently asked questions
When is molality better than molarity?
Molality does not change with temperature because it is based on solvent mass, not solution volume. Colligative-property problems usually use molality.
Why do I need density?
Molarity is per liter of solution, while mass percent and molality are mass-based. Density links volume of solution to its mass so those families of units can be connected.
What if I do not know the formula?
Leave the formula blank and type the molar mass in g/mol directly. The converter only needs M for mole ↔ mass links.
References & further reading
Standards bodies, university open courseware, and peer-reviewed references that align with the methods used on this page.
Keep learning with more calculators and study guides on Online Science Tools.