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BTEC level 3 unit 2A
- Module
- Unit 2A
- Institution
- PEARSON (PEARSON)
Unit 2A, complete coursework, achieved distinction
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Unit 2APart 1- Preparation of Standard Solution
METHOD:
Calibrate the weighing balance that you will be using
Weigh between 1.25 and 1.45g of anhydrous sodium carbonate.
Carefully transfer the sodium carbonate to a large beaker, accurately and
precisely recording measurements to determine the exact mass transferred.
Add 150cm3 of distilled water to the beaker, stir and completely dissolve the
sodium carbonate.
Carefully and accurately transfer all the solution to a 250cm3 volumetric flask, and
make up the solution to 250cm3 with more distilled water.
Apparatus and chemicals needed:
Weighting balance
Weighting boat
Beaker
Distilled water
Glass rod
Volumetric flask
Sodium carbonate
How to calibrate a weighting balance?
Turn on the balance and put into calibration mode, put the weight on the scale and
wait for it to calculate the total weight. If the weight is off, hit the calibration button
and wait for it to recalibrate.
Health and safety:
Wear safety spectacles (goggles) during this experiment because I was making
a solution that involved chemicals.
When calibrating the balance, I made sure the masses were safe and that they
would not fall on the floor.
I made sure that the electrical equipment was kept away from any liquids.
Also, I made sure the glassware was placed in a safe place where it could not
fall off the bench.
Calculating the concentration of sodium carbonate:
, Weighting boat= 1.26g
Weight between 1.25 and 1.45 g
Weighting boat with solid= 2.55g
2.55g - 1.26g= 1.29g
Number of moles of sodium carbonate (Na₂CO₃)
Moles=mass/molecular mass
N= 1.29g/23x2+12+16x3
N= 1.29/106
N= 0.012 moles
Finding the concentration:
Moles=concentration x volume
N= C x V
C= N/V
C= 0.012/0.25
C= 0.048 mol dm3 (concentration of sodium carbonate)
Part 2- Standardisation of an acid
METHOD:
Calibrate the pipette that you will be using.
Carefully and accurately transfer 25cm3 of your sodium carbonate solution into a
250cm3 conical flask and add a few drops of methyl orange indicator.
Clean and fill a burette with a given solution of hydrochloric acid, which will
have a concentration of approximately 0.1M.
Titrate the sodium carbonate solution with the hydrochloric acid, until the
indicator changes colour at the end point.
Accurately and precisely record all measurements to determine the exact titre of
hydrochloric acid required to reach the end point of the titration.
You will need to decide whether the titration needs repeating and how many
times.
Apparatus and chemicals needed:
, Pipette
Conical flask
Methyl orange indicator
Burette
Sodium carbonate solution
Hydrochloric acid solution
How to calibrate a pipette?
First step is to weight the beaker, then use a clean and dry 25 cm3 pipette to suck up
distilled water to the mark of the pipette, do not forget to make sure that the bottom
of the meniscus is also at the mark. Transfer the water to the beaker and weight it,
the mass of the water should be 25.11g, the temperature 20°C and the density at this
temperature 0.99829g/cm3
Using the formula density=mass/volume and now rearranging the formula to find the
volume, volume=density x mass
Volume= 0.99829 X 25.11
Volume=25.06 cm3
Close to the actual volume, 25 cm3
Then, wash the pipette with distilled water and the solution used.
How to calibrate a burette?
First step is to weight the beaker, then use a clean and dry 50 cm3 burette and fill it
with distilled water, do not forget to make sure that the bottom of the meniscus is also
at the mark. Transfer the water into the beaker and measure the mass of the water
should be 50.15g, the temperature 20°C and the density at this temperature
0.99829g/cm3
Using the formula density=mass/Volume
Volume=density X mass
Volume= 0.99829 X 50.15
Volume=50.15cm3
Close to the actual volume of 50 cm3
Wash the burette with distilled water and then wash it with the solution used.
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