Unit 4 - Laboratory Techniques and their Application
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unit 4 assingment 2
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Unit 4 - Laboratory Techniques and their Application
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PEARSON (PEARSON)
I recorded the yield and worked out its mean. I recorded the purity and worked out its mean. Going through every step in your practical or industrial method how it affects the purity and yield or safety. compare the yield of the investigation to the industrial value. advantages of the testing meth...
Unit 4 - Laboratory Techniques and their Application
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Reflex is a method which has a lot of mixture which is used to allow organic substances to be
heated smoothly and the amount of gas or the dissipation of energy that leaves during the
reflux method is very small because it heat the substances very gently and slowly. This is a
process which is used to increase the purity it does that by evaporating and condensing the
distillate. The main equipment is a Liebig condenser it has 2 tubes. One the water goes in
which causes condensation and the other one the water goes out. The water which goes in the
Liebig condenser is important because this is what cools the gases. Vapour that has been
formed when the heating mixture is collected and put in the condenser now I stopped heating
and it change state from a gas back to a liquid so the mixture can properly react.
I heated the flask with an electric mantle because when it is heated with a water bath it is not
suitable due to how hot it can get and this can be a hazard. This is due to the fact of the high
temperature of the water which can cause many hazards such as a burning risk and also the
risk of getting an infection. I added anti bumping granules to the mixture because It is used to
prevent large gases being produced by providing a nucleation site which does the opposite of
producing large gas bubbles it produces small gas bubbles. The anti-bumping granule which
provides the nucleation site is very important that it produces small bubbles this means that
the bubbles do not leave the mixture and also there is not an overflow in the reaction this
cause a stable reaction and a steady boiling point.
Distillation- this is used to differentiate out the mixture or the compound and distillation only
happens in a liquid state and different liquid boil at a different temperature because of the
different properties of the element. In distillation the liquid is also heated gently to make it
into a vapour pressure. Now the liquid is a vapour the pressure of the vapour has to match the
pressure of the atmosphere and when this happens the liquid can boil . The vapour pressure
determines if a liquid has a high boiling point or a low boiling point. The low vapour pressure
means the liquid has a higher boiling point and the higher vapour pressure means the liquid
has a lower boiling point. The flask is gently heated so this can break up or split the mixture
in the compound. Secondly the liquid with the a lower boiling point boils first and the liquid
changes into a vapour. The vapour is heated is too hot so there is an equipment called the
Liebig condenser which stops the liquid from heating too much and also to cool down. When
the vapour cools down it changes into a liquid state because of condensation and also pours
the liquid into the second flask which produces a distillate. However we never did this in our
experiment this is used to increase the purity.
The laboratory making ethyl ethanoate.
1.) In a flask of 125 cm3 I added 25cm3 of ethanoic acid and 25cm3 of ethanol.
2.) Then I added 5cm3 of sulfuric acid in the mixture.
3.) I also added anti bumping granules and this enables the reaction to bubble slowly.
4.) I fitted the flask to a condenser. The condenser has a rubber tubing which enables cold
water to go through.
5.) Now I used an electric mantle which causes the mixture to boil for around 7 to 8 minutes
and a note I heated it gently.
6.) Now I refluxed the mixture which was used to increase the purity of the substance.
7.) Now the electric mantle Is switched off for the mixture to cool.
Purifying the impure ester
, 1.) Now I had a separating funnel where I poured all the impure ester into the
separating funnel and also added 25 cm3 of water and at the end of the separating
funnel there is a stopcock I made sure it was closed. The liquid is poured into the
separating funnel which helps to take out the impurities which are in the ester.
2.) At the stopcock I put a bung at the stopcock and shake the funnel an important note
is that make sure you hold on to your bung this will make sure that the mixture does
not spill when shaking the funnel.
3.) Shaking the funnel enables to separate the aqueous layer from the organic layer in
the separating funnel and I poured down the aqueous layer. Repeat this process
again This makes sure that the impurities which are liquid are poured out from the
mixture.
4.) 5cm3 sodium carbonate I added to the organic layer and I mixed it with the mixture
this makes sure that no gas is seen and this balances the mixture where there is an
acid and neutralises it.
5.) In the separating funnel there Is two layers I poured out the aqueous layer again.
6.) Add 25cm3 of water to the organic layer.
7.) Add 25cm3 of calcium chloride which is used to remove the water.
8.) Pour the mixture which is in the separating funnel into the flask which will give you a
pure ester.
Method for siwoloboff
1.) Pour two thirds of water into a test tube
2.) Fill a sample tube that is dry with liquid to be tested.
3.) Add a capillary tube which is closed at one end and open at the other into the
sample.
4.) Have a rubber band attached to the test tube and putt the thermometer on the
outside of the test tube in the rubber band.
5.) Place sample tube in a water bath and heat it and also stir the water.
6.) When there is vapour or gas bubbles in the capillary tube then switch off the water
bath allowing it to cool.
7.) When there is no more bubbles in the capillary tube and the liquid returns back to
74+75+73/3= 74
My boiling point was 74C and the actual boiling point is 77.1c which shows that the practical
that was done had many impurities and also illustrates that the sample is impure. The results
that I got compare to the actual value and the average shows that the boiling was quite high
compare to the actual value this have might been due to human error. The average boiling
point was 71 degrees this shows that I have 3.1 degree difference and something I could have
done to improve the results to be more accurate like when it says 25cm3 of distilled water, as
I had a higher boiling point my samples were more impure… ethanol or ethanoic acid I
should have taken more care in measuring it to the exact 25cm3 and also for the concentrated
sulfuric acid I could have taken it more slowly with the pipette measuring it slowly and
carefully to minimise the risk of a hazard.
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