Unit 2- Practical Scientific Procedures and Techniques
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2A, Standard solution distinction peice of work
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Unit 2- Practical Scientific Procedures and Techniques
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PEARSON (PEARSON)
These are the assignments I wrote for Unit 2 last year as a BTEC applied science student. I got a distinction, D, and full mark in each assignment; if requested, I can show the proof. I worked very hard on those assignments and each. I am sure these assignments, if used correctly will give you the ...
Unit 2- Practical Scientific Procedures and Techniques
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(Keeping up the standards)
A short while ago I was assigned to a large chemical plant called Chemcalequip.
The plant was often asked to perform different practicals and as a part of my
role, I had to - guarantee that all of the used equipment were calibrated. In
addition I have to ensure that the equipment and chemicals in the practicals are
safe and ready for use. The report will mainly focus on titration and colorimetry
principles using standard solutions. I will deeply explain the techniques, analyse
and evaluate the results, and lastly give some suggestions for improvements.
Standard solution
The purpose of this practical was to know what a standard solution is and how to
prepare it. Another thing is to understand the concept of moles, concentration
and dilution.
Equipment list : 2.65 g of sodium carbonate ( Na2CO3), a balance, a 500 cm³
beaker, weighing boat, distilled water, a volumetric flask and funnel.
Risk assessment : Sodium carbonate 1 can irritate the eyes in high concentrations
of fumes. Therefore, you should have goggles on your eyes to reduce the risk. The
chance of something going wrong is quite low if you are paying attention, but if
you are not careful many things that were not dangerous can become
dangerous.
Firstly any equipment we use during the experiment has to be calibrated before
use. In this experiment we have to calibrate the balance ( weighing scale ) before
weighting the sodium carbonate.
Calibration equipment list:
● 4 different known weights. For example 4 different sizes of plastic cups with
known weights that have been measured before using a calibrated
balance.
● A balance with 1 decimal.
● A pen and paper or a laptop to record the results.
Calibration method :
1. First of all make sure that the balance is well stabilised .
, 2. Start the balance and then press the T button.
3. Put the smallest plastic cup of the known weight on the balance.
4. Record the shown weight
5. Calculate the difference between the known weight and the weight that the
balance showed.
6. Repeat the trial 3 more times with the other known weights.
Results:
Known weight (g) Reading on balance (g)
25.0 24.9
35.0 34.9
45.0 44.9
55.0 54.9
Analysis:
The pattern that we can see here is a reading off by 0.1 g. This uncertainty is a
little bit more than the smallest uncertainty of the instrument, which is 0.05g. That
means that the balance is almost like new, but still needs to be calibrated to
know the smallest uncertainty of it to measure the sodium carbonate that we
need accurately. We can conclude that the balance was calibrated a short time
ago, which is expected in schools. This will not affect the accuracy so much, but a
little bit. I have to keep in mind that the balance shows a weight that is one gram
less than the actual weight. What I have to do to make sure that this off reading
doesn't affect my results is to add one gram to the weight that the balance will
show. In this experiment the required amount of sodium carbonate is 2.65 g, so
when the balance shows 2.64 g is then you have the right amount of sodium
carbonate.
What I could do better in this calibration is to use 4 known weights that were
measured on a calibrated balance. If you just use a finished product and expect
it to be as heavy as it is mentioned in the package then your results will not be
reliable. More profits is the reason behind that. Many finished products have less
weight than the one that is mentioned and this is why you have to weigh your
known weights on another balance that is calibrated before you use them to
calibrate this balance. I could also do more trials to get more results. This would
lead to a better accuracy of the calibration, because I have more data to
compare between.
Method :
, 1. We put the weighing boat on the balance and had to tare it.
2. 2.65 g of sodium carbonate was accurately weighed putting the smallest
uncertainty of the balance in mind.
3. Pure the sodium carbonate in the weighing boat, which still is on the
balance.
4. We transferred the content to a beaker and added a very little amount of
distilled water to the weighing boat to get rid of the remnants of the
sodium carbonate.
5. Pour the water with sodium carbonate remnants into the beaker. The water
should be less than 250 cm³. The less water you use the better it is.
6. Pour the solution now to the volumetric flask.
7. Add some water if the solution did not hit the line 250 cm3. Make sure that
the bottom of the meniscus is at 250cm3 and not the top of it.
8. Finally, close the volumetric flask, shake it moving the content up and down
to make sure that it has been mixed properly. Another way to mix the
content is using a stirring rod moving it in circular movements.
9. Label the volumetric flask with your name.
Results:
This means that the concentration in a 0.25 dm3 solution that contains 2.65 g of
sodium carbonate is 0.1 mol/ dm3 .
Calibration of pH metre:
As well as the other equipment, the pH metre has to be calibrated. This
calibration is different from the last calibration. Every equipment has its own way
to be calibrated in, which is done to keep the effectiveness and the accuracy of
the equipment.
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