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 ;)
PREPARATION OF ASPIRIN
Synthesis of Aspirin
We followed a set of instructions on the sheet given to us in order to carry
make a pure sample of aspirin and calculate it’s % purity, % yield and atom
economy. When preparing aspirin, we mixed 2.0 g of 2-hydroxybenzoic acid
(salicylic acid) with 4 cm3 of Ethanoic anhydride then added 5 drops of
concentrated sulphuric acid. After the crystals appeared and later formed crystal
mush, we diluted it in ethanoic acid and dried it in ice. We then filtered off the
crystals and put the filtrate in boiling water to dissolve. We reserved some
crystals for further testing. We recrystallized the rest of the crystals and filtered it
after we let it cool. It is important to recrystallize the aspirin because the reaction
may contain by-products and they need to be removed to obtain pure aspirin. If
these instructions were followed properly and all possible errors were avoided,
we would be able to come out with 100% pure aspirin.
ESTIMITING PURITY
Iron chloride test
This is one of the following methods we used to test purity of aspirin. By
following the instructions on the sheet, we added 2 cm3 of distilled water to 4
different test tubes that we labelled. To one tube we added one crystal of the
aspirin we made before recrystallization and shook it. Then to another test tube,
we added one crystal of the crystalized aspirin we made and shook it. To another
test tube, we added one crystal of 2-hydrobenzoic acid and shook it. Then to the
last test tube, we added one crystal of known pure aspirin and shook it. Lastly, to
each test tube, we added 2 drops of neutral iron (III) chloride solution and shook
it. If the product is pure aspirin, it should turn yellow and the ones with impurities
would be dark purple.
Melting point determination
The melting point of aspirin was taken as another means to identify, and test
the purity of the product. We set up the apparatus as demonstrated by our
teacher and we heat the oil at a rate of 1 to 2 degrees per minute as we
approached the melting range of the sample. We used a capillary tube with one
sealed end and filled it up with the sample then melted the under end. After that,
we placed the tube inside the melting point apparatus and increased the
temperature slowly while recording the temperature. To avoid errors, didn’t heat
the oil for too long. The melting point of aspirin was not consistent with the
literature value which is 135 degrees Celsius while ours was 135 degrees Celsius.
This shows that the synthesised aspirin was not pure.
Thin Layer Chromatography (TLC)
Chromatography is a physical method used to separate mixtures of coloured
substances. We set up the apparatus as demonstrated by our teacher and
followed the following instructions to analyse and check the purity of aspirin
using TLC. Using a pencil, we drew a line across the plate about 1 cm from the
bottom and top. Then we marked 4 equally spaced points on the line drawn at
the bottom of the plate and placed a small drop of each of the different samples
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Waley. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.99. You're not tied to anything after your purchase.
