Standard level
Neutralisation is the reaction between an acid and a base forming a salt and water. Most neutralisation reactions are exothermic, but there are exceptions.
Background
This activity will allow the students to compare the energy change when different acids and bases undergo neutralisation. The solutions of dilute acids do not have an exact concentration and will be used in excess. In this way the base is the limiting reagent and may be used to calculate the number of moles involved in the reaction.
The specific heat capacity of the mixture is approximated to that of water, 4.18 kJ kg-1 K-1.
sodium hydroxide + hydrochloric acid
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
sodium hydroxide + ethanoic acid
NaOH(aq) + CH3COOH(aq) → CH3COONa(aq) + H2O(l)
Chemicals
- Hydrochloric acid, 2M
- Sulfuric acid, 1M
- Ethanoic acid, 2M
- Sodium hydroxide(aq), 2.0 mol dm-3
- Potassium hydroxide(aq), 2.0 mol dm-3
Apparatus
- Polystyrene beaker and lid
- Glass beaker, 250ml
- Pipette, 25ml
- Pipette filler
- Measuring cylinder, 50ml
- Temperature probe (or thermometer)
- For each acid-base combination
- Using the 25ml pipette, transfer 25cm3 of the sodium hydroxide(aq) to a pre-weighed polystyrene beaker supported in a 250ml beaker.
- Record the temperature of the sodium hydroxide solution.
- Fill a measuring cylinder to 30cm3 with the acid under investigation.
- Record the temperature of the acid.
- Pour the acid into the sodium hydroxide solution and record the highest temperature attained.
- Weigh the polystyrene beaker, lid and reaction mixture.
- Repeat two more times.