My friends and I did it together, we also looked over it with a science teacher with a degree in chemistry and she said it was worthy of a distinction. PS: Don't copy word for word ;)
In all the experiments we carried out, we recrystallized our products to purify
them effectively. The recrystallization technique we used involved dissolving our
product in water, along with the impurities it contained to be purified. This can
work effectively because our product crystalizes and separates from the
impurities because due to the fact that the impurities don’t reach their limit of
solubility and thus stay in solution. This method can still give rise to errors
because the balance of water and product is very important and need to be
maintained. The higher the volume of water you add, the less the impurities you
will have left after recrystallization also decreasing the mass of your end product.
However, if you add too little water, there would be impurities remaining in the
solution after drying it. If this technique is done properly, the mass of the useful
product would not be affected while purifying it. After using this technique when
preparing aspirin we calculated our % purity to be 80%. From looking at the data,
the experiment was somewhat efficient and reliable because only 20% of the
final product was the impurities. One of the reasons why this technique of
purification is very effective is because the product can easily be purified again.
After the product is recrystallized, it is left to cool and dry, however, this process
allows the dried crystals of the product to be recrystallized further and become
purer.
THIN LAYER CHROMATOGRAPHY (TLC)
The thin layer chromatography is a technique we used to separate mixtures of
coloured substances. We placed components of our samples on different points
on a plate and placed it inside a solvent, then observed the distance each
sample travelled under a UV light. After carrying out the TLC experiment and
recording the distances travelled by each sample, we were able to determine the
Retention factor (Rf) values for the pure, recrystallized and crude sample as well
as the limiting reagent. After carrying out this experiment, we calculated the R f
value for our recrystallized and pure aspirin which turned out to be the
same. This indicates that our recrystallized aspirin was pure. Although, this
experiment says that our product was pure, the results of the melting point and
iron (III) chloride test indicate the presence of impurities in our recrystallized
product. The TLC method is greatly viable rather than the iron (III) chloride test
as this method relies on numerical data gotten from our readings while the iron
(III) chloride test relies on colour changes which can sometimes be hard to
detect.
Distance travelled by thecompund
RF = Distance travelled by the solvent front .
MELTING POINT
The melting point of aspirin was taken in order to identify, and test the purity of
the product. After setting up the apparatus, a sample of our product was slowly
heated at a rate of 1 to 2 oC per minute using a bulb. We then recorded the
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