.Table 1 : shows the substances being tested in the experiment.
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In order to make sure that the substances present above were Strong or weak a PH test was conducted and the results are shown below in Table 2:
Table 2 : Shows the Ph values of each substance an d then concludes the strength of each substance.
Valid Test:
In this experiment a number of precautions are going to be put in place in order to make this as fair a test. They are listed as follows:
1) Make sure each volume of acid is 40 cm3.
Explanation: By keeping the volume of each acid and alkali at a constant level the only variable in each experiment will be the strengths of each acid and alkali and nothing else.
2) Make sure that the same type (same area and same material) of cup is used in place of each experiment.
Explanation: Again by insuring that the same type of cup is used in each experiment it removes variables such as surface area from each experiment.
3) The cup is placed in a beaker, when swirling the two mixture in the cup care must be taken in order to ensure that one does not put ones hand around the beaker as this may warm up the mixture in the beaker from the body heat which is generated. It is therefore advisable to use the thermometer in order to mix the substances.
Explanation: This again is put in order to ensure that extra heat does not affect the experiment in any way and the only variable is the strengths and weakness of each acid or alkali.
4) When measuring the temperature change make sure the temperature rises to its maximum and then drops and settles before it is recorded – this would give added precision.
The theory behind this experiment.
Theory Behind Neutralisation
In simple terms, neutralisation is the reaction between an acid and base. It is a formation of bond between the H+(aq) from the acid and OH-(aq) from the base:
H+(aq) + OH-(aq) H2O (l)
This is an exothermic reaction due to that fact that bond-forming processes liberate energy this will release heat to the surroundings which will result to a temperature rise. By using the temperature change in each mixture after the reaction the heat of neutralisation will be calculated. The heat of neutralisation “ of an acid by a base is the amount of heat liberated when one mole of hydrogen ions (H+(aq))from an acid reacts with one mole of hydroxide ions (OH-(aq)) from a base.”*
OH-(aq) OH-(aq) OH-(aq)
Table of Results:
Some Safety Points
Whilst doing the experiment some safety points had to be considered as shown below:
- Firstly at all times safety goggles were worn – to prevent any chance of these chemicals coming in contact with the eyes
- It was advisable to have good ventilation in the room where the experiment was being conducted. This is because it was found that Ammonium Hydroxide has a very potent smell.
- The chemical Sodium Hydroxide is corrosive therefore, hands must be washed carefully.
- The thermometer in use during the experiment was a mercury thermometer therefore extra care was taken in order to not break it.
