Unit 4 - Laboratory Techniques and their Application
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LEARNING AIM C: EXPLORE MANUFACUTING TECHNIQUES AND TESTING METHODS FOR AN ORGANIC SOLID
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Unit 4 - Laboratory Techniques and their Application
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PEARSON (PEARSON)
Prepare and test the purity of an organic solid and draw conclusions. Aspirin is the given organic solid which we are going to make, crystalise and then purify as part of this assignment. We will crystallise and re-crystallise the solid. What is crystallisation? Crystallisation is the process to re...
Unit 4 - Laboratory Techniques and their Application
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ASSIGNMENT C
, HAJRAH ALI (40157986) UNIT 4 - ASSIGNMENT C 2020-10-12
C.P5 CORRECTLY PREPARE AND TEST THE PURITY OF AN ORGANIC SOLID AND DRAW CONCLUSIONS
Aspirin is the given organic solid which we are going to make, crystalise and then purify as part of this assignment.
We will crystallise and re-crystallise the solid.
What is crystallisation? Crystallisation is the process to reform crystals and to disappear and appear (re-
crystallisation).
What is re-crystallisation? It is the most used organic chemistry laboratory technique for the purification of
solids.
Synthesis of Aspirin is prepared using 2-hydroxybenzecarboxylic acid also known as salicylic acid and ethanoic
anhydride as shown by the rection equation:
The
first
part of
producing Aspirin is to measure using a mass scale and boat and to measure and tare
each separatly, and then add 8 drops of phosphiric acid slowly so that the product
does not char and then dissolve a small amount of substance in a miniumum amount
of liqiuid (solvent) at a hot tempearture and to keep stiring it using a glass rod which
will help the solid disssolve. The liquid should be at a hot temperature so that the
solvennt is able to dissolve because if it is cold the product will not disolve as it would
be impossibke and will not be able to recrystilise too. A small amount of solvent is
used which allows the product re-crystiliilse later on if too much solvent is present it
will make it difficult for the aspirin crystals to re-crystilise. This is done by a hot water
bath rather than a bunsen burner for safety precautions as ethanol is a flammable
product which Is not ideal to use in an open labortory instead a fume cupboard is
used if the solvent is toxic. So we you a hot water bath and kettle water to help
quicken the process. Acid Reflux is when an organic synethes often requires heating
of a long time to achieve a complete dissolution of stubborn solutes, we condense and re-collect the solvent vapour
in the boiling flask so that we do not lose any volume whilst we boil the liquid. We used a refulxed condenser which
was opened from the top to prevent pressuristaion or an expolsion which would potentially lead to an injury. The
colling region would allow the sample to re-condesne and fall back into the boiling flask, which is held in place by a
clamp. A water hose should also be attached and water should be flowing through the outer jacket which will re-
condense the vapour and send it back to the location. Its effect in volume should stay the same at 0, and it could be
done for fours, says and signifciantly long periods without signifcant loss of volume benefit. We used a Filter funnel
with filter paper. Hot filtration is used so that when hot hits cold dissolved crystals will precipitate out and will re-
crystallise in the funnel alongside impurity which is not good. Pour mixture and will separate from liquid and
insoluble impurities. We use hot filtration to ensure that the aspirin does not crystallise and to only filter out the
insoluble impurities. Separate product from soluble impurities by cooling it down and then putting it in an ice bath
and crystals will crystalise and stir solution with glass rod so crystal will re-crystallise, use an ice bath because the
solubility of crystals will be much lower at a lower temperature so crystals to make sure that crystals do not dissolve
and be sure that the do re-crystallise. Pour solution and crystals into a Buchner funnel and attached to a vacuum
(vacuum filtration) and leave it to dry, we used a Buchner funnel because it produces a relatively quick and produces
a relatively dried product rather than using a Bunsen burner because the crystals will become thermally unstable and
would be most likely to break. There is no need to dry just leave them in a warm room.
Substances we used:
o 2-hydroxybenzoic acid (1g)
o Ethanoic anhydride (2cm3)
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