Volumes used in concentration calculations must be in dm3, not in cm3. It is useful to know that 1 dm3 = 1,000 cm3. This means:
For example, 500 cm3 is 0.5 dm3 (500 ÷ 1,000). It is often easiest to convert from cm3 to dm3 before continuing with a concentration calculation.
The relative formula mass, Mr, of the solute is used to convert between mol/dm3 and g/dm3:
To convert from mol/dm3 to g/dm3, multiply by the Mr.
Calculate the concentration of 0.100 mol/dm3 sodium hydroxide solution in g/dm3. (Relative formula mass: NaOH = 40.0)
concentration = 0.100 × 40.0
= 4.00 g/dm3
Calculate the concentration of 7.30 g/dm3 hydrochloric acid in mol/dm3. (Relative formula mass: HCl = 36.5)
Concentration = 7.30/36.5
= 0.200 mol/dm3