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Unit 22 – Assignment 3 – P5
Analysis of iron Supplement tablets
Method:
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Weigh two tables
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Use a funnel to transfer the paste formed into a 100cm3 volumetric flask
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Make up to the mark using 1M sulphuric acid
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Titrate 10cm3 portions of the solution formed with 5
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The endpoint is when the solution turns pale pink
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9g

Calculating the mass of iron(II) sulphate in each tablet:
The following reaction occurs in the titration:
MnO4- + 5Fe2+ + 8H+ --> Mn2+ + 5Fe3+ + 4H2O
Mean titre of MnO4- = 19
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005 x 19
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7 x 10-5
Mol of Fe2+ in titration = 9
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85 x 10-4
Mol of iron(II) sulphate = (4
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004
Mass of iron(II) sulphate in tablet = (4
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9 = 0
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Weigh out between 2
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50g of powdered malachite into a 100cm3 beaker and add
about 10cm3 of 1M sulphuric acid
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Warm the beaker on a hot plate until the fizzing stope
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Use a funnel and filter paper to transfer the solution to a 50cm3 volumetric flask
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Rinse out the filter funnel with distilled water, adding the washings to the volumetric flask
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Make up to the mark using distilled water
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Allow solution to cool
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The copper (II) sulphate solution produces can be analysed using spectrophotometry
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Use 1M copper(II) sulphate solution, pipettes and volumetric flasks to prepare solutions of
copper sulphate with the following concentrations: 0
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0750M, 0
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125M and
0
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2
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1M sulphuric acid as the reference
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Then find the absorbance of the solution prepared from the ore
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149 x 50) / 1000
= 0
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007 x 159
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189

% Purity = (1
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/2
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845%

Unit 22 – Assignment 3 – M5 & D3
Analysis of iron Supplement tablets
An error could occur whilst grinding the tablets in the pestle and mortar
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Also, when transferring the paste,
some of the it may be left behind
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To improve the method, put pressure on one tablet at a
time
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If you have to, put your hand
over the mortar whilst you are grinding the tablets, this means that there would be little to none
wastage of the tablets and therefore reduce the error
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This could be caused by parallax error
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So when adding the acid to the volumetric flask, the bottom of the meniscus must be on the
line
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This would then cause the titration to be inaccurate as
the solution would turn pink at a different time
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To improve the method add the solution slowly
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This means that you will get an
accurate reading and therefore reduce the error
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If too much solution
was added then we would get a incorrect volume reading
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This would cause the recording to be inaccurate,
invalid and unreliable
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Whilst you are doing that, swirl the flask to mix up the solution
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As soon as it does turn pale
pink, turn off the tap
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In addition, if someone did not use a spotting tile under the flask, we may misinterpret when the
colour actually changes, or what colour the solution is
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For example, if the person was colour blind
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To improve
the method, put a spotting tile under the flask
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This means that you will get an accurate reading and
therefore reduce the error
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If the glassware
was not washed or dried properly and there was leftover solution, it would contaminate and dilute
the solution causing the recordings to be inaccurate, invalid and unreliable
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This means that you will get an accurate
reading and therefore reduce the error
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722g
Group 2 - 0
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77469g
Group 4 – 0
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651g
Group 6 - 0
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62g

As you can see in the results, my results were more accurate than Group 7
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An error could have occurred when releasing the solution into
the volumetric flask
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This can be cause by turning the tap all the way, so that the solution falls at a fast rate
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Whereas in my group, during
the titration, we slightly turned the tap so it was only dripping out the solution
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Once it started to turn pink, we turned off the
tap, swirled it, if it turned back we carried on adding the solution
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This means that we got a more accurate reading and therefore reduce the error
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This is because I had a lesser mass of product at the
end
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An error could have occurred in my experiment whilst
grinding the tablets in the pestle and mortar
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Also, when transferring the paste, some of it could have
been left behind
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Whereas Group 7 could have taken more care when
grinding the tablets; putting their hand over the mortar whilst grinding the tablets, this means that
there would be little to none wastage of the tablets
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For example, Group 7 has only used two decimal places, whereas Group 6 has
recorded their result in seven decimal places
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Analysis of Copper ore (Malachite)
An error could occur when transferring the malachite
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This would cause the results to be invalid and
unreliable
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Also use a spatula to scrape
it off the sides of the beaker
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Also, when measuring the weight of the malachite, some could get on the top pan balance instead of
in the weighing boat
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Also, when transferring the
malachite from the weighing boat to the beaker, someone may breathe on it and mass would be
lost
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This
would cause the results to be invalid and unreliable
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If some of the malachite goes on the top pan balance, start this step again
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This means that you will get an accurate reading
and therefore reduce the error
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This could be caused by parallax error
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So when adding the water to the volumetric flask, the bottom of the meniscus must be on the
line
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This would cause the recordings to be inaccurate and
the experiment to be invalid and unreliable
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Whilst
you are doing this, look at the flask at eye-level so you can be sure that you have added the right
amount, once the bottom of the meniscus has fallen on the line
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Furthermore, errors could occur by contamination of the solution, or dilution with water
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To improve
the method, make sure the glassware is clean and has no liquid in it
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In addition, if there was leftover solution in the beaker or on the filter paper, when rinsing it with
distilled water, the solution will be less concentrated
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To improve the method, wash the filter
paper with the distilled water until it is clear
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This means that you will get an accurate reading and therefore reduce the
error
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This would cause the recordings to be inaccurate and the experiment to
be invalid and unreliable
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This means that you will get
an accurate reading and therefore reduce the error
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Or if we did not label our glassware, we would not know which
glassware held which concentrated solution
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To improve the method, use different pipettes for each
solution, Then after you use them, put the pipette in front of the conical flask which hold the same
solution
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If necessary, mark them so that you do not mix them
up
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Other results:
Group 1: 62%
Group 2: 64
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67%
Group 4: 45%
Group 5: 34
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32%
Group 7: 60
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70%
Group 10: 62
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This is because I had a
greater mass of product at the end
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If some of the malachite was still left
in the weighing boat or on the side on the beaker, or if they spilt some, then their concentrations
and recording of the absorbance would be inaccurate
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Whereas in my group, we made sure all the malachite was used
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This means that we got a more accurate reading and
therefore reduced the error
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This is because I had a lesser mass of product at the
end
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An error could have occurred in my experiment if we
were using the same pipettes when transferring difference concentrated solutions
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Or if we did not label our glassware, we would not know
which glassware held which concentrated solution
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Whereas Group 2, they would have used
different pipettes for each solution, Then after each use, they could have put the pipette in front of
the conical flask which held the same solution and ensured that they did not mix them up
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This means that they had
a more accurate reading and therefore reduced the error
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For example, Group 8 has only used two significant figures, whereas Group 2 has

recorded their result in 4 significant figures
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