This is coursework for Unit 2 Practical Scientific procedures and techniques and is Learning aim A - Titration. This was graded a DISTINCTION with NO FEEDBACK. Work is to an optimum level. Good luck with writing!
Part 1 - Preparation of a Standard Solution
The weighing boat was placed on the balance and its mass was noted down which was 3.01g. The
balance was then set to 0g with the weighing boat still on the balance and sodium carbonate was
added inside the boat until the balance reached 1.34g. This was the mass of the sodium carbonate.
Both the weighing boat and sodium carbonate had a total mass of 4.35g.
The sodium carbonate inside the weighing boat was emptied into a beaker accurately and precisely.
Approximately 150cm^3 of distilled water was added to the beaker and stirred until the sodium
carbonate was completely dissolved. Once dissolved, the solution was poured into a 250cm^3
volumetric flask using a funnel. Once used, distilled water was used to rinse the beaker, stirrer, and
funnel to make sure no remains of sodium carbonate were left on them. More distilled water was
added until the meniscus touched exactly 250cm^3 on the flask. Then a stopper was placed on the
volumetric flask.
Mass of weighing boat 3.01g
Mass of boat with sodium carbonate 4.35g
Mass of sodium carbonate 1.34g
The number of moles of sodium carbonate in the solution was determined by using the formula
Moles = Mass / Mr. The Mr of sodium carbonate (Na2CO3) is 106. Therefore, the number of moles of
sodium carbonate dissolved in 250cm^3 is 1.34/106 = 0.013. The number of moles were calculated
so as to use the solution to standardise the hydrochloric acid.
Calibration of a balance
Weight Mass on balance
1 1.022
2 2.0032
2 2.0031
5 5.0056
10 10.0055
20 20.0077
50 50.0153
100 100.0101
Part 2 – Standardisation of an acid
Calibration of the pipette
Firstly, a 25cm^3 pipette was calibrated. Then distilled water was sucked into the pipette until it was
precisely 25cm^3. The distilled water was transferred into a beaker on the weighing balance set to 0.
Then the mass of the water was recorded. This was repeated five times. The most accurate mass of
water calculated was 24.86cm^3. In order to work out volume, the equation volume = mass x
, density was used. According to (Water - Density, Specific Weight and Thermal Expansion Coefficients,
2022) the density of water at 20C is 998.21kg.
24.86*0.99821 = 24.82cm^3 – This is close enough to the 25.00cm^3 to be used for the experiment
and has a 99.28% accuracy.
Volume of water /cm^3 Mass of water /g Accurate volume
Thereafter the burette was calibrated. A clean flask was weighed. Then distilled water was poured
into the burette until 0.00cm^3. The distilled water was then dispensed into the flask underneath
until the bottom of the meniscus rested on 50.00cm^3. The most accurate mass of water turned out
to be 49.85. Again, in order to work out volume, the equation volume = mass x density was used.
According to (Water - Density, Specific Weight and Thermal Expansion Coefficients, 2022) the density of
water at 20C is 998.21kg.
49.85*0.99821 = 49.93 – This is close enough to the 50.00cm^3 to be used for experiment.
To start, a rough titration was carried out to familiarise ourselves with the process and to ensure
accuracy for the actual experiment. The rough titration also gave an idea of what the final result
would come out to in order to make the experiment easier.
Using a pipette, 25cm^3 of the sodium carbonate solution was taken out carefully and accurately.
The solution was then transferred into a conical flask and a few drops of methyl orange indicator
was added to it.
After that, into a burette, approximately 0.1M of hydrochloric acid was added. The conical flask with
the sodium carbonate was placed under the burette and the solution was titrated with the
hydrochloric acid. A stirrer was used to mix the solution as it was being titrated. As we could begin to
see a slight change in colour, the HCl was slowly added drop at a time until the indicator in the
conical flask fully changed colour. We observed it change colour from orange to pink.
The final volume of the HCl was recorded. The titration was repeated in the exact same manner until
there were three similar results within 0.1cm^3 apart from each other. The mean of the results was
calculated to average it out and improve accuracy and precision.
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