How it works

A useful distinction

Dilution preserves the solute amount

For the same dissolved solute mass and molar mass, doubling final solution volume halves molarity. Compare two volume entries to see dilution clearly; changing the concentration does not mean the original amount of solute has disappeared.

Using solution volume in concentration calculations

For 5.844 g of a pure solute with molar mass 58.44 g/mol, the amount is 0.1 mol. At a final solution volume of 1 L, the concentration is 0.1 mol/L; at 100 mL it is 1 mol/L. Final solution volume means the volume after dissolving, not the solvent poured in beforehand. Keep mass, molar mass, and volume units consistent. Mass-fraction ppm and ppb conversions additionally require solution density; the tool does not assume every solution has water's density.

Molarity: formula and assumptions

Molarity = mass/(molar mass×solution volume).

Use final solution volume, not solvent volume before dissolving.

Required mass: formula and assumptions

Mass = molarity×molar mass×volume.

Assumes pure solute and the specified molar mass.

Find volume or molar mass: formula and assumptions

Volume=mass/(molar mass×molarity); molar mass=mass/(molarity×volume).

Use final solution volume and a known pure-solute mass.

Concentration & solution units: formula and assumptions

Molarity = mass / (molar mass × final solution volume). Mass concentration = mass / volume.

Prefixes and units are converted independently. Mass-fraction ppm/ppb require entered solution density; water density is not assumed. Mass concentration alone cannot identify molar mass.

Worked example

Using the Molarity example:

Inputs

Solute mass (g): 5.844
Molar mass (g/mol): 58.44
Solution volume (L): 1

Method

Molarity = mass/(molar mass×solution volume).

Result

Example result

Molarity: 0.1 mol/L

These are illustrative inputs. Change the values to explore a different scenario.

Formula references

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions

Should I enter solvent volume before dissolving the solute?

No. Molarity uses the final solution volume, which need not equal the starting solvent volume.

Why is solution density required for mass-fraction ppm or ppb?

A mass fraction relates solute mass to solution mass. Density connects solution mass with volume; the tool does not assume water density.

Can a mass concentration alone identify molar mass?

No. Converting mass to moles needs molar mass or independent molar-concentration information. Mass concentration alone does not identify the substance.

Prepared by Finflo. See our methodology and editorial policy.

Molarity Calculator

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