Standard level
Titration involves adding one reagent to another until the equivalence point, which is usually indicated chemically. However, there are other ways to identify this point, one of which is by measuring the energy change. This is called thermometric titration.
Background
The law of conservation of energy. one consequece of the law is the extensive nature of energy, i.e the energy change in any process is directly proportional to the amount of matter involved.
As acid is added to base, or vice versa, the energy released causes the temperature of the mixture to increase. This continues with each addition until the equivalence point, after which the temperature decreases as cold reagent is added to the reaction mixture.
This type of titration needs the acid and base to be relatively strong, in terms of concentration, to ensure that the energy release is large enough to change the temperature.
Chemicals
- Hydrochloric acid(aq), HCl, 2.0 mol dm-3
- Sulfuric acid(aq), H2SO4, 1 mol dm-3
- Sodium hydroxide(aq), NaOH, 2.0 mol dm-3
Apparatus
- Burette, 50ml
- Polystyrene beaker
- Glass beaker, 250ml
- Thermometer or temperature probe
- Pipette, 25ml
- Pipette filler
- Using a pipette, transfer 25ml of sodium hydroxide solution, 2.0 mol dm-3, into a polystyrene beaker supported in a 250 ml glass beaker.
- Record the temperature of the sodium hydroxide.
- From a burette, run 5.0 ml of dilute hydrochloric acid into the sodium hydroxide stirring with the thermometer. Record the highest temperature reached.
- Continue adding 5ml aliquots of HCl(aq), recording the highest temperature after each addition, until 40 ml have been added.
- Repeat the process twice more to obtain more reliable results.
- Perform the procedure again, using ethanoic acid, 2.0 mol dm-3, and sulfuric acid, 1 mol dm-3, instead of hydrochloric acid.
- Sodium hydroxide(aq), NaOH, 2.0 mol dm-3, is caustic and will burn the skin.
- Hydrochloric acid(aq), HCl, 2.0 mol dm-3 is corrosive and will burn the skin.
- Sulfuric acid(aq), H2SO4, 1 mol dm-3 is corrosive and will burn the skin.