Analysis of Aspirin tablets

Evaluation

Bayer Aspirin Cardio had stated that its commercial preparation would have about 100 mg (0.10 g) of aspirin. Now according to my calculations, their tablets had an average mass of 0.13 ± 0.01 g and the % of aspirin present in their tablets was 98.26 ± 10.53%. Keeping in mind the uncertainties involved, I can still say that they did have 0.10 g of aspirin in their tablets. This statement of mine is based on the calculations that if we take the average mass to be the least possible value which is 0.12 g and if we take the % of aspirin present also to be the least possible value which is 87.73%, the amount of aspirin present would work out to be around 0.10 g.

o Working

(87.73/100) x 0.12 = 0.10 g

Aspirin Aspar had stated that its commercial preparation would have about 300 mg (0.30 g) of aspirin. Now according to my calculations, their tablets had an average mass of 0.34 ± 0.01 g and the % of aspirin present in their tablets was 97.25 ± 4.04%. Keeping in mind the uncertainties involved, I can still say that they did have 0.30 g of aspirin in their tablets. This statement of mine is based on the calculations that if we take the average mass to be the least possible value which is 0.33 g and if we take the % of aspirin present also to be the least possible value which is 93.21%, the amount of aspirin present would work out to be around 0.30 g.

o Working

(93.21/100) x 0.33 = 0.30 g

According to the above calculations, I have reached the conclusion that to find out which is the best value for money, I would have to look at their market price rather than the % of aspirin present in them because they are nearly the same percentage. Bayer Aspirin Cardio was offering 30 tablets for Kenya Shillings 190. Thus the value of one tablet worked out to be Sh 6 ⅓. On the other hand, Aspirin Aspar was offering 100 tablets for Kenya Shillings 150. Thus the value of one tablet worked out to be Sh 1½. Therefore buying Aspirin Aspar tablets made more economical sense.

An experimental error could be calculated for both the aspirins, but since the % of aspirin it contained was quite near to 100% and also keeping in mind the varying uncertainties involved, the experimental error value would be negligible.

The method was fairly easy and straightforward. The mass of the tablet could have changed from its original value during weighing, etc. because the tablet is made of powder which can get rubbed off easily. A systematic error was that the 10 cm3 pipette had a zero error, a form of calibration. If an uncertainty was present, the final calculations could have been more accurate. The readings were mostly precise which helped later in the calculations. Multiple readings were taken and average readings were processed when a difference of ±0.1 occurred so as to reduce the random errors. However human parallax error can be added to random errors.

When using the pipette for measuring and transferring the alcohol to the conical flask, the pipette filler used for sucking in air was not tightly held by the pipette. Therefore this made the solution pour from the pipette once it was measured to its required amount. To improve on this, the pipette filler used to suck in the alcohol should be properly fixed so that no air escapes from the pipette filler. Another error that could have risen in the experiment is the change in the absolute value of the content of the conical flask. This is because during stirring, some water might have hung on to the side of the flask and when titrated, that value of solution might have not been accounted for.

The apparatus used for the experiment was easy to operate and set up. Time was managed well as the initial results obtained were within the ± 0.10 cm3 range and thus fewer repetitions were needed.

One of the major assumptions made during the experiment was that the mass of the tablet weighed was the actual mass of the tablet. Another assumption was that when the indicator color changed to pink, at that exact moment the addition of sodium hydroxide solution was halted and this was repeated for the second brand of Aspirin too. These were the major weaknesses in the calculations as failing to obtain absolute values resulted in a final calculation that lacked accuracy. Therefore although precise values were obtained, they might have not necessarily been accurate.

Certain modifications that could be made are that the burette could be washed with distilled water after every trial and then rinsed with sodium hydroxide solution. More accuracy could be obtained if the figures were not rounded up to two decimal places, but for the sake of uniformity, they were rounded up. Including an uncertainty for the 0.10 mol dm-3 sodium hydroxide solution would also aid the overall accuracy of the calculations.

If all apparatus had a stated uncertainty on them, the calculations could become more accurate. Also even if in the initial trials a difference of ± 0.10 cm3 is obtained for the required sodium hydroxide solution, more repetitions could assert the exact value of the solution needed to produce the color change of the indicator and thus the overall random errors could be reduced.

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