Essay
Assignment 1 Unit 15 - Practical Chemical Analysis
- Institution
- PEARSON (PEARSON)
A Distinction-graded assignment on quantitative analysis.
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By: nancieequestrian • 5 months ago
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Unit 15: Practical ChemicalAnalysis Tutorial Booklet
A: Investigate quantitative
analysis on the components of
matrices to determine their
composition.
, The Percentage of copper in brass
(by reacting with acid and using
colorimetry)
The aim of this experiment was to find the percentage of copper in brass, to do this we had to perform 2 experiments. O
which was dissolving the brass in nitric acid, which resulted in a copper nitrate solution. The next, we then made differen
concentrations of copper sulphate solution. After that, we then put all the solutions in cuvettes and put them into a colo
and drew a graph of results. The method we used for dissolving the brass in nitric acid was as follows:
1)We weighed out around 0.3g of brass, on a scale which started at 0.01g. Our result for t
was we had measured 0.33g of brass on our 2nd experiment (this shown on the picture on
left). Then, put this in a 25cm³ beaker.
2)In a fume cupboard, we then added 5cm³ of 5M Nitric Acid using a plastic pipette. Then
put the beaker on a hot plate, which was kept in the fume cupboard. We could have used
graduated pipette instead ensuring that we used 5cm³ of nitric acid and not too little or to
much.
3)On the hot plate, we warmed the mixture up to about 60°C. Then, after all the brass has
dissolved, we turned off the hot plate and left the beaker to cool.
4)We then transferred the solution to a 10cm³ volumetric flask. Then add a few drops of w
to the beaker and transfer the washings. We transferred the washings to ensure that we
hadn’t left any of the solution behind in the beaker on the funnel.
5)After transferring the washings, we had added extra water to the meniscus line. We the
the stopper in the top of the flask and inverted it (turned it upside down and then right w
up) about 4 or 5 times to make sure that the solution was properly mixed. We did this to
ensure that the solution was properly mixed.
, Photos of dissolving the brass in nitric acid
For this practical we had
twice. This was because
did it the first time, the s
evaporated and left a so
bottom of the beaker, an
didn’t fully dissolve. This
because we had turned
too high, causing the sol
solid. This could be due
evaporating, or the hydr
oxygen molecules formin
and then evaporating fro
solution. This is shown in
row of photos. However
time we performed the
we made sure not to rise
up too high. It worked o
better and it didn’t go w
second time. This is show
bottom row of photos.
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