Mass concentration

A solution contains a solute dissolved in a liquid. Its mass concentration tells us how much solute is present in a given volume of the solution. A more concentrated solution contains more solute in the same volume.

Mass concentration is commonly measured in grams per cubic decimetre, $$\mathrm{g/dm^3}$$. For example, a concentration of $$4\ \mathrm{g/dm^3}$$ means that each cubic decimetre of solution contains $$4\ \mathrm{g}$$ of solute.

Calculating mass concentration

Divide the mass of solute by the volume of the solution:

For example, if $$8\ \mathrm{g}$$ of solute is dissolved to make $$2\ \mathrm{dm^3}$$ of solution:

If the concentration and volume are known, the relationship can be rearranged to find the mass of solute:

For instance, $$2\ \mathrm{dm^3}$$ of a solution with a concentration of $$4\ \mathrm{g/dm^3}$$ contains $$8\ \mathrm{g}$$ of solute.

Changing mass concentration

At the same solution volume, increasing the mass of solute increases the concentration. With the same mass of solute, increasing the solution volume decreases the concentration: the solute is spread through a larger volume. Conversely, the same mass of solute in a smaller volume gives a more concentrated solution.