Concentration and titrations · Grade 9
The concentration of a solution tells you how much solute is dissolved in each dm³ (litre) of it. It can be given in g/dm³ or in mol/dm³. In a titration, a burette adds one solution to a measured volume of another until they just react, shown by an indicator changing colour. The volumes and the balanced equation then give the unknown concentration.
Key facts
- 1 dm³ = 1 litre = 1000 cm³: divide a volume in cm³ by 1000 to get dm³.
- concentration (g/dm³) = mass (g) ÷ volume (dm³).
- concentration (mol/dm³) = moles ÷ volume (dm³), so moles = concentration × volume.
- To change mol/dm³ into g/dm³, multiply by the Mᵣ.
- In a titration a pipette measures one solution (often 25.0 cm³) into a flask, and a burette adds the other until the indicator changes colour: the end point.
- Repeat until the titres are concordant (within 0.10 cm³ of each other) and use their mean.