Molarity Formula Guide
Chemistry Tools | May 20, 2026 | 10 min read
How to use M = n/V, convert volume, prepare solutions, and avoid common concentration errors.
| Need | Use | Formula |
| Molarity | moles and liters | M = n/V |
| Moles | molarity and volume | n = M x V |
| Dilution | stock to working | M1V1 = M2V2 |
| Mass | prepare from solid | g = M x V x molar mass |
Definition
Molarity is moles of solute per liter of solution. The solution volume is the final total volume, not the amount of solvent poured in. This distinction matters when preparing solutions in volumetric flasks.
The equation M = n/V is simple, but most mistakes come from units. Volume must be in liters, and moles must represent solute particles or formula units according to the problem.
Preparing a Solution
To prepare a solution from a solid, calculate moles from M x V, then convert moles to grams using molar mass. Dissolve the solid in less than the final volume, transfer to a volumetric flask, and dilute to the mark.
For example, a 0.100 M NaCl solution in 1.000 L requires 0.100 mol NaCl. With molar mass 58.44 g/mol, the mass is 5.844 g.
Dilution
Dilution problems use M1V1 = M2V2 because moles of solute stay constant while volume changes. Stock solutions are concentrated; working solutions are usually more dilute.
The volume you solve for is the volume of stock solution to measure, not the amount of water to add. Water is added until the final volume reaches the target.
Useful Site Tools
Use the Molarity Calculator for concentration, moles, mass, and dilution work. Use the Molarity List note for ranked formulas, unit conversions, and preparation examples.