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Unit 19 - Practical Chemical Analysis Assignment 3 (Pass)
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- PEARSON (PEARSON)
This achieved the pass criteria.
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Assignment 3 - ChemistryOver the period of three weeks (17/01/2020 – 27/01/2020) Level 3 BTEC Applied Science (Forensic Science)
Group B students carried out three separate chemistry practicals regarding spectroscopy. The first practical I
carried out alongside Bethan Williams was the Colorimetric Determination of Copper Ore on 17th January
2020.
Colorimetric Determination of Copper Ore.
Aim
For the best possible outcome to be achieved from the colorimetric determination there are two aims which
must ideally be achieved, these are; to practise using a colorimeter and to prepare a calibration curve so that
samples of unknown concentrations are able to be plotted.
Introduction
Certain beverages and foods consist of artificial colours which have direct links in relation to behaviour
changes. Over recent years there’s been increasing evidence which states that food colouring causes reflux,
hyperactivity, and gas in children. Researchers have examined the impact of six artificial colourings, which are;
yellow, blue, red, carmoisine, tartrazine, and ponceau. During the examination it was established that the
activity of the children who consumed a mixture of these colourings was measurably affected. Certain food
industries have already started acting in removing colourings from foods and supermarkets have also
introduced labelling on products which are free from artificial colourings. Certain colourings have even been
found to artificially enhance sportsmen performances and at certain levels these performance enhancing
additives have been banned.
Safety & Hazards
To ensure an individual is safe throughout this practical there are control measures which have been sternly
put in place and must be followed, these control measures are as follows;
A laboratory coat and safety goggles are mandatory to be worn by an individual during this practical,
to ensure no hazardous substances encounter the skin. A laboratory coat and safety goggles also are
enough to take account of the most hazards as well as risks deemed significant.
It’s important that immediately after use waste is placed in labelled containers, where waste can then
be correctly disposed of by a scientific technician.
A good laboratory practice is remined of for a safe working environment to be maintained.
Corrosive = Sulphuric Acid
Method
1. Firstly, 1g of the unknown substance needs to be weighed into a beaker and 10cm 3 of H2SO4 (sulfuric
acid) added. This must be carefully adding ensuring that the mixture doesn’t go over the top of the
beaker.
2. Next, once the reaction has finished, the mixture must be filtered into a conical flask.
3. Then, deionised water must be added until the volume of the liquid in the flask is 100cm 3.
4. A standard solution of Copper Sulphate is provided. A calculation must be carried out to establish how
much solid must be weighed out in order to make up 250ml of a 0.1mol dm -3 solution? (How this was
worked out will be explained shortly.)
5. When the calculation had been completed it needed to be checked with Dr Emma Morgan before
continuing.
6. Finally, by using this new solution as a standard, four dilutions need to be prepared using certain
volumes.
Results
To make the standard solution the amount of solid required must first be weighed out. The standard solution
will be made to a concentration of 0.1 mol dm -3 and to a volume of 250ml. The process for finding out the
amount of solid needed is as follows:
Volume ÷ 1000 x Concentration = Moles
=250 ÷ 1000 x 0.1 mol dm-3
1
, Assignment 3 - Chemistry
=0.25 x 0.1 mol dm-3 = 0.025 moles
Mr of CuSO4 •5H2O
Cu= 63.5
S= 32.1 = 63.5 + 32.1 + 64 = 159.6
O= 16 x 4= 64
H= 1.01 x 2= 2.02
O=16=
=2.02 + 16=18.22
=18.02 x 5
=90.1
90.1 x 159.6 = 249.7 Mr
Moles x Molar mass = Mass
Mass = 0.025 moles x 249.7 = 6.2425g = 6.24g
After preparing the standard solution I had to prepare a dilution, and this was done by carrying out the
following calculation:
C1V1=C2V2 C 2 = (C1 x V1) ÷ V2
C1= 0.1 mol dm-3
V1= 20 cm3, 40 cm3, 60 cm3, 80 cm3, 100 cm3
C2 = Concentration in Question
CuSO4 (cm3) 100 80 60 40 20
H2O (cm3) 0 20 40 60 80
Concentration of 0.1 0.08 0.06 0.04 0.02
Dilution (mol
dm-3)
V2 = 100 cm3
100 cm3 = 0.1 mol dm-3 x 100 cm3= 100/100= 0.1mol dm-3
80 cm3 = 0.1 mol dm-3 x 80cm3 = 80/100= 0.08 mol dm-3
60 cm3 = 0.1 mol dm-3 x 60cm3 = 60/100= 0.06 mol dm-3
40 cm3 = 0.1 mol dm-3 x 40cm3 = 40/100= 0.04 mol dm-3
20 cm3 = 0.1 mol dm-3 x 20cm3 = 20/100= 0.02 mol dm-3
Now that we know the concentration of each sample (besides the unknown) the absorbance of each solution
needs to be measured using a colorimeter. The absorbance measurements obtained are displayed in the table
below:
Sample Concentration Absorbance
1 0.02 0.11
2 0.04 0.20
3 0.06 0.30
4 0.08 0.38
5 0.1 0.49
Unknown 0.086 0.42
2
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