F.6 Chemistry TAS/Experiment 3/P.()
PLK TANG YUK TIEN COLLEGE
ADVANVED LEVEL CHEMISTRY (TAS)
EXPERIMENT 3
Analysis of Two Brands of Commercial Bleaches
Objective
To determine the concentration of sodium chlorate(I) (NaClO) in two commercial bleaches and compare the two bleaches on both concentration and price.
Procedures
- 10.0 cm3 of the bleach “KAO” was pipetted into a clean 250 cm3 volumetric flask. It was made up to the mark using deionized water.
- 25.0 cm3 of the diluted solution was pipetted into a conical flask.
- 10 cm3 of 1 M potassium iodide solution and 10 cm3 of dilute sulphuric acid was added into the conical flask also.
- The mixture in the conical flask was titrated against the 0.0992 M sodium thiosulphate solution.
- Three drops of freshly prepared starch indicator are added into the conical flask when the reaction mixture turned pale yellow .
- The mixture was titrated to the end-point.
- At the end point, the solution turned from dark blue to colourless.
- Steps (1) to (7) were repeated with another bleach “LION”
Results
Concentration of standard sodium thiosulphate solution : 0.0992M
Brand 1 Trade Name : KAO Bleach Price : $7.33per dm3 ($11/1500mL)
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Peer Reviews
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Quality of writing
Grammar, spelling and punctuation to an high standard. Good, clear format.
Level of analysis
The candidate should include in their introduction why they are examining sodium chlorate(I) in their experiment, such as what significance this has to the action of the bleach. The procedure is recorded very clearly and would be easy to follow. The questions are answered to a very high level of detail and the calculations are all correct. Decimal places lack consistency in places.
Response to question
The response to the question is done to a very high level. With the combination of accuracy and scientific detail the experiment is flawless in calculations. The improvements would be to add an evaluation of where the experiment could have been improved and what errors may have occurred to show an understanding of how the experiment went.