Molarity (C = n/V)

Also known as moles per litre · concentration from moles

C = \frac{n}{V}

Worked example: 2 mol in 4 L → 0.5 mol/L — press Try an example to run it live, then adjust anything.

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Molarity (C = n/V) explained

Molarity answers the practical question "how much stuff is in this bottle?" by counting moles of solute per liter of solution. Dissolve 58.44 g of table salt — exactly one mole of NaCl — in water and top up to the 1.00 L mark of a volumetric flask, and you have a 1.00 M solution. Note the fine print: it is per liter of solution, not per liter of water added, which is why chemists fill to a calibrated mark instead of adding a measured liter of solvent.

Molarity is the workhorse concentration unit because reactions are mole-to-mole affairs: multiplying C by a dispensed volume immediately gives the moles delivered, which is exactly what a titration calculation needs. Physiological saline is about 0.154 M NaCl, ocean water roughly 0.5 M, and concentrated hydrochloric acid around 12 M — a span that dilution calculations cross daily in every lab.

Molarity (C = n/V) formula

C = \frac{n}{V}

Where

$C$ = Molar concentration (M)
$n$ = Amount of solute (mol)
$V$ = Volume of solution (L)

Missing one of these? Work it out first, then come back

Molar concentration — Osmotic Pressure (Π = MRT), Beer–Lambert Law (A = εbc)
Amount of solute — Molality (b = n/m), Mole Fraction
Volume of solution — Mixing Two Solutions (C₁V₁ + C₂V₂ = C_f V_f), Pounds of Active Chemical in a Tank

Part of this formula set

Ways to express concentration

6 formulasMolarity, molality, mass percent, mole fraction, normality and the dilution equation — six answers to “how much solute is in there?”