- Only a little acid is needed as it have a strong intermolecular forces.
2) surface area of the evaporating dish
- the surface area used is the same that is in the petri dish.
3) concentration of the acid
- The concentration used for the acid is the same that is 0.1M
4) temperature
- the temperature for the water bath is fixed to 60°c
5) air humidity
- the experiment was carried out in the same place that have the same humidity
MATERIALS AND APPARATUS
Table 1: list of apparatus and material used
METHOD
-
Prepare the water bath machine at the temperature of 60.00C
- Then, prepare a 1ml of 0.1M HCl in an evaporating dish, using a measuring cylinder.
- Quickly, put the evaporating dish on the water bath machine, and start taking the time until the 1ml acid fully evaporates using the stopwatch.
- Record the time taken for the acid to evaporate.
- Repeat the experiment one more time to get average reading.
-
Then, repeat steps 1 until 5 by using H2SO4 and H3PO4 instead of HCl.
- Tabulate the data in a table.
DATA COLLECTION
- Qualitative data
- The solution become less from time to time
- Solution of sulphuric acid evaporates fastest
- The last solution to evaporates is hydrochloric acid
- Quantitative data
Table 2: time reading for the solution to evaporates
DATA PROCESSING
Average =
Table 3: average time and rate of evaporation of acids
Calculation for the uncertainties are:
HCl = [(0.125/1.000) + (0.1/47.5)] × 100%
= 12.71%
H3PO4 = [(0.125/1.000) + (0.1/41.2)] × 100%
= 12.74%
H2SO4 = [(0.125/1.000) + (0.1/35.2)] × 100%
= 12.78%
Hence, the rates of evaporation of the acids are:
Table 4: rate of evaporation with uncertainties
Graph 1 : rate of evaporation of different liquids
LIMITATIONS AND SUGGESTIONS
Limitation
- The water loss is difficult to see when it is fully evaporate
- It takes a long time for the solution to fully vaporised.
- Other factors also affect the rate of evaporation.
Suggestion
- Put some coloured liquid so that it is easily to be seen or take the mass fot a certain time as the main measurement instead of taking time as the measurement.
- Increase the surface area of the exposed petri dish to the water vapour.
- Air movement also affect the rate of evaporation. So, that lid of the water bath should be closed in order to the control only one factor, that is temperature.
CONCLUSION
Hydrochloric acid is the acid with the lowest rate of reaction compared to the other two acids, phosphoric acid and sulphuric acid. This is because HCl is a strong acid. It dissociates easily in water to form hydrogen and chloride ions. Strong acid means that HCl has strong covalent bond. So, it requires a lot of energy to break the bonds between the hydrogen and chloride ions.
Hence, the hypothesis is accepted.