Unit 2- Practical Scientific Procedures and Techniques
Instelling
PEARSON (PEARSON)
BTEC Applied Science Unit 2 Assignment A - Titration and Colorimetry. Results, graphs, evaluation all included. Referenced throughout. Assignment has been awarded a DISTICTION.
Unit 2- Practical Scientific Procedures and Techniques
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Unit: 2 Practical Scientific Procedures and Techniques
Keeping up the standards
Titration
Introduction
Titration is an experiment where the reactants are accurately mixed in the correct proportions by
achieving a solution containing salt and water only as a conclusion, where the products are neutral
(pH 7). In this experiment, the aim is to determine the concentration of a sample of sodium
hydroxide accurately and skilfully.
Calibration
Calibration is a process that ensures pieces of equipment used for measuring are portraying a
precise measurement. This is a very important procedure because if the equipment is displaying
inaccurate values, it can make the whole experiment erroneous and imprecise. Additionally, there
are many different methods that can be used to calibrate pieces of equipment such using accurate
masses and by using water.
In the experimentation, there are 3 pieces of equipment that need to be calibrated and these are
the weighing scale, the burette, and the bulb pipette.
Weighing scale
To calibrate the weighing scale a range of accurate masses need to be used. The weights could have
a mass of 0.1g, 1.0g, 10g, and 100g. These need to be placed one by one on the weighing scale using
tongs as the mass of the weight as they will otherwise have a change in mass. Additionally, if the
reading shown matches the actual mass of the weights, then the weighing scale can be used for the
titrations. However, if the reading does not match the actual mass, then the weighing scale will need
to be fixed using a collaboration key. In this case, the calibration of the weighing scale was done by
an external organisation so that it would be more exact as it was very hard to be done without any
direct contact to the masses
Burette
The density of water is used to calibrate a burette. The burette would be rinsed with some distilled
water and dried to ensure that there is no contamination from previous practical’s that may affect
accuracy. While rinsing the burette, the tap would also be checked so that it wouldn’t affect the
calibration later. Some distilled water would be poured into the burette and the tap would be
opened to let some water exit to ensure the tip of the burette would contain water and there would
be no air bubbles. The distilled water would be left to sit in the burette for 1 – 2 minutes to make
sure all water has reached the bottom and no water left on the sides. Additionally, once all the water
would be in one place, the reading where the bottom of the meniscus would be laying would be
recorded. Furthermore, the mass of a beaker would be measured and written down so that later it
can be subtracted from the total mass. The distilled water would be poured into the beaker and
measured using a weighing scale and the mass of the beaker would be subtracted. Lastly, the value
would then be converted into a value that could be compared to the reading that was previously
shown on the burette.
Bulb Pipette
The density of water is also used to calibrate a bulb pipette. The bulb pipette would be rinsed with
some distilled water and dried to ensure that there is no contamination from previous practical’s
that may affect accuracy. The distilled water would be poured into the pipette making sure the
meniscus would lay on the engraved line. Furthermore, the mass of a beaker would be measured
and written down so that later it can be subtracted from the total mass. The distilled water would be
, poured into the beaker and measured using a weighing scale and the mass of the beaker would be
subtracted. Lastly, the value would then be converted into a value that could be compared to the
reading that was previously shown on the pipette.
Standard Solution – (NaHCO3)
A standard solution is required while carrying out titration because it is important that one of the
reactants concentration is known. This is required as precise and reliable results are only
accomplished when there is an exact concertation of the standard solution.
Equipment List
1 x Weighing boat – Used as a container for NaHCO 3 when measuring the amount need on
the weighing scale
Weighing scale – Utilized to measure 2.1g of NaHCO 3
Sodium Hydrogen Carbonate – Needed to make a standard solution for the titration
Beaker – Used as a container to mix the NaHCO 3 and distilled water
Distilled water in a wash bottle – Required to produce a standard solution for the titration
Glass rod – Used to mix the NaHCO3 and the distilled water together
250cm3 Volumetric flask – Where the NaHCO3 solution is stored
Spatula – To pour some NaHCO3 powder into the weighing boat
Method
Make 250ml of a 0.1M solution of sodium hydrogen carbonate.
0.1M = 0.1 mol dm-3 Mass Number
Na = 23
NaHCO3 → 250mL H=1
(23 x 1) + (1 x 1) + (12 x 1) + (16 x 3) C = 12
O = 16
23 + 1 + 12 + 48 = 84 (Mr)
Concentration = Moles ÷ Volume → Moles = Volume X Concentration
0.1 x 0.25 = 0.025 moles
Moles = Mass ÷ Mr → Mass = Moles x Mr
0.025 x 84 = 2.1g
1. Firstly, the mass of the weighing was measured by placing it on the weighing scale, and the
reading that was shown was written down on a piece of paper, which was needed to check
whether all the sodium hydrogen carbonate was moved to the beaker afterwards.
2. Once the reading was written down on a piece of paper, the ‘Tare’ button was pressed to zero
the value shown. The ‘Tare’ button may also be shown as ‘T’ or ‘O/T’ or ‘Re-zero’.
3. Furthermore, sodium hydrogen carbonate was added into the weighing boat using a spatula
until it reached 2.1g.
4. The 2.1g of sodium hydrogen carbonate was then moved into the beaker from the weighing
boat. The weighing boat was then placed back onto the weighing scale to check if all the sodium
hydrogen carbonate was placed into the beaker as mentioned previously.
5. Next, distilled water was added to the beaker using a wash bottle and stirred with the sodium
hydrogen carbonate using a glass rod until all the solid particles were dissolved. If this wasn’t
done properly then the mass would have been affected. Therefore, it was needed to be done
accurately.
6. The solution was the transferred into a 100cm 3 volumetric flask by placing the glass rod into the
neck of the volumetric flask and then pouring it. Any spillages were needed to be avoided or else
the concentration of the solution was going to be affected making the experiment incorrect.
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