Quantitative analysis is used by chemists to make measurements and calculations. Alkalis neutralise acids to make salts and water. Their concentration can be analysed using titrations.

A solution forms when a solute dissolves in a solvent. The concentration of a solution is a measure of the amount of solid dissolved in 1 dm^{3} of solution. When the mass of solute dissolved is measured in g, the units for concentration are g/dm^{3}.

concentration (g/dm^{3}) =

- Question
8 g of sodium hydroxide is dissolved in 2 dm

^{3}of water. Calculate the concentration of the sodium hydroxide solution formed.concentration =

concentration =

= 4 g/dm

^{3}

Apparatus used to measure volumes is usually marked in cm^{3} or ml. Although these are different units, they describe the same volume. For example, 250 ml = 250 cm^{3}.

Volumes used in concentration calculations must be in dm^{3}, not in cm^{3} or ml. It is useful to know that 1 dm^{3} = 1,000 cm^{3}. This means:

- divide by 1,000 to convert from cm
^{3}to dm^{3} - multiply by 1,000 to convert from dm
^{3}to cm^{3}

For example, 250 cm^{3} is 0.25 dm^{3} (250/1,000). It is often easiest to convert from cm^{3} to dm^{3} before continuing with a concentration calculation.

- Question
100 cm

^{3}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 in dm

^{3}= = 0.1 dm^{3}concentration =

=

= 5g/dm

^{3}