A solution forms when a solute dissolves in a solvent. The concentration of a solution is a measure of how 'crowded' the solute particles are. The more concentrated the solution, the more particles it contains in a given volume.
The concentration of a solution can be calculated using:
The units for concentration are also shown as g/dm3, but this means the same as g dm-3.
8 g of sodium hydroxide is dissolved in 2 dm3 of water. Calculate the concentration of the sodium hydroxide solution formed.
Apparatus used to measure volumes is usually marked in cm3 or ml. Although these are different units, they describe the same volume. For example, 250 ml = 250 cm3.
Volumes used in concentration calculations must be in dm3, not in cm3 or ml. It is useful to know that 1 dm3 = 1000 cm3. This means:
For example, 250 cm3 is 0.25 dm3 (250 ÷ 1000). It is often easiest to convert from cm3 to dm3 before continuing with a concentration calculation.
100 cm3 of dilute hydrochloric acid contains 0.5 g of dissolved hydrogen chloride. Calculate the concentration of the acid in g dm-3.
volume of acid = 100 ÷ 1000 = 0.1 dm3
concentration of acid = 0.5 ÷ 0.1
= 5 g dm-3