Calculations:
CH3COOC6H4COOH (s) + 2NaOH (aq) → HOC6H4COONa (s) + H2O(aq)
Conclusion:
The aim of our experiment was to “find the mass of acetyl salicylic acid in an aspirin tablet and compare it with the manufactures claim.” The mass of acetyl salicylic acid the manufacture claims is in an aspirin tablet is 300mg. From our experiment we calculated that the mass of acetyl salicylic acid was 360mg. This was a percentage deviation of 20%. From the manufactures claim.
There is no way of telling if the manufacture is telling the truth about how much acetyl salicylic acid is in the tablets so there is no way of telling how completely accurate or our experiment was but it is far more likely that the manufacture is correct. Our fairly small random error of 2.39% does not cover the 20% deviation so the rest of the error must be systematic error.
Evaluation:
A problem with this experiment was that when crushing the 4 aspirin tablets in the crucible although distilled water was used to wash most of the aspirin into the beaker not all of the powder was washed into the beaker. Some powder was unavoidably left in the crucible which meant that our results would have proved inaccurate because there would not have been as much CH3COOC6H4COOH to react with the NaOH. This is not consistent with our results but was systematic error and would have affected our results.
Another problem was that there may be other chemicals in the aspirin that could have reacted with the NaOH as well as the CH3COOC6H4COOH. This could have meant that we could have calculated more CH3COOC6H4COOH when the NaOH was in fact reacting with other chemicals as well.
The titration trials were very consistent with only 0.2 mls separating the lowest and highest values. This shows that the titration was consistent but not necessarily accurate because we used a slightly faulty burette that maintained an air bubble at the bottom. This would have accounted for some of the systematic error.
Improvements:
An improvement that we could have made was we could have tested the mass of CH3COOC6H4COOH in more than just 4 tablets. To get a more accurate result it would have been better if we had done the experiment another ten times and with different packets of the same brand of aspirin tablets to see if the mass of CH3COOC6H4COOH is consistent in different packets.
An improvement we did make was we used a magnetic stirrer during titration so that the reactions were sped up so it was easier to see if the chemicals had completely reacted.
Another improvement that we could have implemented was using a water bath to keep the temperature the same over the whole experiment. The experiment was carried out over 2 days and in those three days the weather was different which could have affected our results.