# Investigation of the Energy Created by a Neutralisation Reaction.

### Investigation of the Energy Created by a Neutralisation Reaction

Planning

2M HCl
1M H2SO4
2M CH3CO2H
2M NaOH
2M NH4OH

A neutralisation reaction is the process in which the acidity or alkalinity of a substance is destroyed. Destroying acidity means removing the H+ (aq) ions by reaction with a carbonate metal or a base. Destroying alkalinity means removing the OH- (aq) ions by reaction with an acid. The acid and alkali particles must be in exactly equal amounts to get a perfectly neutral solution.
If a bond is broken, energy is needed and the reaction is endothermic. However Neutralisation is an exothermic reaction. This means it gives out energy to the surroundings in the form of heat. This obviously means there will be a rise in temperature.

NEUTRALISATION

acid + alkali = salt + water

H+(aq) + OH-(aq) = H20 (l)

In exothermic reactions, DH is negative. The products are at a lower energy than the reactants. In exothermic reactions, the energy released in bond formation is greater than the energy used in breaking old bonds. To work out DH, the equation that should be used is DH = m x s x DT where m = mass, s = specific heat capacity of water (4.2 J/k/g), DT = change in temperature (initial – final).

• A strong acid: Produces a high concentration of H+ ions in a water solution. Eg. Hydrochloric acid. (HCl) This has a pH of about 1.
• A weak acid: Produces a low concentration of H+ ions in a water solution. Eg. Ethanoic acid. (CH3CO2H) This has a pH of about 3.
• A strong alkali: Produces a high concentration of OH- ions in a water solution. Eg. Sodium hydroxide. (NaOH) This has a pH of about 14.
• A weak alkali: Produces a low concentration of OH- ions in a water solution. Eg. Ammonia solution. (NH4OH) This has a pH of about 12.
• INPUT VARIABLES
• The concentration of the acid.
• The concentration of the alkali.
• The starting temperature of the acid.
• The starting temperature of the alkali.
• The pH of the acid.
• The pH of the alkali.
• Volume of either acid or alkali.

OUTCOME VARIABLES

• Change in temperature.
• The pH.
• The time taken.

I am going to look at the energy change when reacting a strong acid with a strong alkali, a weak acid with a weak alkali, a weak acid and a strong alkali and a strong acid and a weak alkali.

RISK ASSESSMENT

All chemicals must be used carefully, and all experiments should be conducted with extreme care. Here are some points that must be followed.

• Safety goggles must be worn at all times.
• Good ventilation is required – some chemicals, eg. Ammonia solutions have very potent smells.
• Sodium hydroxide is corrosive. Wash hands carefully and thoroughly.
• Hydrochloric acid and ethanoic acid are irritants.
• Handle the thermometer with care – it contains mercury, which is poisonous.
• Handle all glassware with care – it may be hot after the reaction has taken place.

FAIR TEST

These points should be followed to ensure the experiment is fair.

• Make sure only one input variable is changed at a time.
• Make sure the ...