Solution concentration is a comparison of the amounts of solute and solvent.

Describing a solution as "stong" or "weak" gives some comparison of the amounts of solute and solvent, but it is only a general idea. Even the terms "dilute" and "concentrated" do not give enough information to make quantitative calculations. To be able to compare solutions quantitatively, "how much" solute and solvent must be known.

The most common units of solution concentration involves moles.

Molarity (M) = moles of solute per cubic decimeter (dm³) of solution.

Remember the following:

• Volume refers to the volume of the total solution, not just the volume of the solvent.
   
• One cubic decimeter (dm³) = 1000 cm³ = 1 liter = 1000 ml