Units of solution concentration

Concentration expresses how much solute is present in a given volume of solution. The volume is the volume of the complete solution, not just the solvent.

Concentration can be expressed using either mass or amount of substance:

• $$\mathrm{g/dm^3}$$ means grams of solute per cubic decimetre of solution. For example, $$2\ \mathrm{g/dm^3}$$ means that each cubic decimetre of solution contains $$2\ \mathrm{g}$$ of solute.
• $$\mathrm{mol/dm^3}$$ means moles of solute per cubic decimetre of solution. For example, $$0.5\ \mathrm{mol/dm^3}$$ means that each cubic decimetre of solution contains $$0.5\ \mathrm{mol}$$ of solute.

Both units describe solute in a volume of solution, but they measure the solute differently: $$\mathrm{g/dm^3}$$ uses its mass, while $$\mathrm{mol/dm^3}$$ uses its amount of substance.