In this assignment you will read about how to correctly prepare and standardise solutions for colorimetry, the method used, results and an overall conclusion and to determine the concentration of copper (II) sulfate using colorimetry. Due to COVID and lockdown we did not carry out a titration exper...
UNIT 2: PRACTICAL SCIENTIFIC PROCEDURES AND TECHNIQUES [40157986 - HAJRAH ALI. MANDEEP MANGAT] APRIL 21
A: UNDERTAKE TITRATION AND COLORIMETRY TO DETERMINE THE CONCENTRATION OF SOLUTIONS.
CONCENTRATE ON KEEPING UP YOUR STANDARDS
A.P1 CORRECTLY PREPARE AND STANDARDISE SOLUTIONS FOR TITRATION AND COLORIMETRY. / A.P2 INVESTIGATE THE CONCENTRATION OF
UNKNOWN SOLUTIONS, USING PROCEDURES AND TECHNIQUES IN TITRATION AND COLORIMETRY.
I. Preparation: Clean the scale and check if it is in a working condition and have accurately calibrated reference weights available.
II. Eccentricity Test: Is carried out to test the effect of the location.
III. Repeatability Test: When the load is several times, results may differ from the original; to find out the repeatability of this
instrument a repeatability test is done. The certified mass is repeated 4 times and then a mean mass is calculated.
IV. Weighing Test: This is carried out to test the accuracy of the weighing instrument through its whole range with increasing and
decreasing weights.
[RESULTS]
CALIBRATION OF WEIGHING SCALES (g) MEAN MASS (g)
CERTIFIED MASS 1 2 3 4
200g 199.96 g 199.95g 199.95g 199.5g 199.95g
20g 19.99g 19.99g 20.00g 19.99g 19.99g
10g 10.00g 10.00g 9.99g 9.99g 9.99g
100g 99.98g 99.96g 99.96g 99.96g 99.96g
Action after calibration: If the reading is within tolerance limits, you do not need to take further action. If the reading is outside
these limits, then you need to adjust.
[CONCLUSION]
Our results show that they are within tolerance of a maximum of 0.05+ - tolerance and is very close to the certified mass weight.
There may have been a human error, which could be the reason why the weights did not show measurements accurately as our
hands may have had collected dirt and oil so, when picking up the weights these may have affected them overall. To prevent this
from occurring we could have used tweezers to pick up the weights, but due to their availability we had to compromise and use our
hands instead.
STANDARD SOLUTION [METHOD]
I. Calibrate the weighing balance that you will be using.
II. Weigh approximately between 1.25 and 1.45g of copper (II) sulphate. Tare [zero] the balance with the empty weighing boat. Keep
the lid on the copper (II) sulphate when not in use to prevent contamination.
III. We Transferred carefully to a beaker and dissolved it in water, to wash out your weighing boat, to ensure all the powder is
transferred. We only need enough water to dissolve the solute. Do not put more than 100cm 3 of water (less is better) stir and
completely dissolve the copper (II) sulphate.
IV. Transfer our solution carefully to a volumetric flask and then washed out the stirring rod as well to ensure all the solution is
transferred.
V. We accurately and precisely record measurements to determine the exact mass transferred.
VI. We Carefully and accurately transfer all the solution to a 100cm 3 volumetric flask and make up the solution to 100m 3 with more
distilled water and read from the bottom of the meniscus. we made sure we did not put more than 100cm3 of water.
, UNIT 2: PRACTICAL SCIENTIFIC PROCEDURES AND TECHNIQUES [40157986 - HAJRAH ALI. MANDEEP MANGAT] APRIL 21
[CONCLUSION]
A volumetric flask has graduated lines which will allow us to measure the volume accurately of the liquids. When reading the
volume, you will look at the bottom of the meniscus that is sitting on the graduated lines. To weigh the substance, we used a
weighing boat rather than filter paper because it will allow transfer of powder to another vessel as it has a smooth surface with
rounded corners which provides protection and pouring it in will be much easier. It also protects the scale tray. We rinse the boat
with distilled water to make sure that all the required substance will transfer over to the other vessel. We made sure that it was fully
soluble in water and stirred the solution with a glass rod, the substance should be pure and not have been mixed with any other
chemical substance. We made sure that it was on a flat surface and that the scale was turned on and was zero, we then made sure
that it was calibrated by using a certified weight on the scale and waiting for the total weight, to make sure if this was not correct,
we would recalibrate it.
DETERMINING THE CONCENTRATION OF COPPER(II) SULFATE SOLUTION BY COLORIMETRY. [METHOD]
I. Calibrate the weighing balance that you will be using.
II. Weigh between 2.50 and 2.70g of hydrated copper (II) sulphate (CuSO 4 .5H2O).
III. Carefully transfer the hydrated copper (II) sulphate to a beaker, accurately and precisely recording measurements to determine
the exact mass transferred.
IV. Add 25cm3 of hot distilled water to the beaker, stir and completely dissolve the hydrated copper (II) sulphate.
V. Carefully and accurately transfer all the solution to a 100cm 3 volumetric flask and make up the solution to 100cm 3 with more
distilled water.
VI. You have made a stock copper (II) sulphate solution of approximately 0.1M. Calculate the precise concentration and label the
volumetric flask.
VII. Using some of the stock copper (II) sulphate solution you have made, dilute so that you have four other solutions of
approximately 0.08M, 0.06M, 0.04M and 0.02M. Calculate the precise concentration of each solution that you make.
VIII. Select an appropriate colour filter and calibrate the colorimeter (or visible spectrometer) that you will be using with the stock
solution and distilled water, according to the manufacturer’s instructions.
IX. Measure and record the absorbance (or transmission) of each copper (II) sulphate solution (approximately 0.1M, 0.08M, 0.06M,
0.04M, 0.02M) and for distilled water (0.00M) using the calibrated colorimeter (or visible spectrometer).
X. Plot a calibration curve of absorbance (or transmission) against the concentration of copper (II) sulphate.
XI. Measure and record the absorbance (or transmission) of Sample A and Sample B (the unknown concentrations of copper (II)
sulphate solution supplied by your supervisor.
XII. Using the calibration curve, determine the concentrations of Sample A and B.
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