Bleach Analysis

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DESIGN Research Question Which of the two commercial brands bleaching solutions, KAO and Swashes is better buy? Introduction Sodium hypochlorite is the most basic ingredient in most commercial bleaches. Amount of this ingredient can be estimated by titration. Sodium hypochlorite reacts with an excess amount of potassium iodide in the presence of acid: ClO- (aq) + 2I- (aq) + 2H+ (aq) I2 (aq) + H2O (l) + Cl- (aq) The amount of iodine given out can be found by titrating with a standard solution thiousulphate solution: I2 (aq) + 2S2O32- (aq) 2I- (aq) + S4O62- (aq) Information of two brands of bleaching solutions: Brand | Price ($) | Volume of bleach (cm3) | Volume of bleach (dm3) | Price per dm3 ($) | KAO | 13.9 | 1500 | 1.5 | 9.27 | Swashes | 14.5 | 2000 | 2 | 7.25 | Variables: Independent variable: Two different brands bleaches Dependent variable: Volume of thiosulphate solution used Controlled Variables | Reason of controlling | How to control? | The molarity of sodium thiosulphate solution (0.065M) | Using different molarity of the solution in each titration will affect the result the experiment. The only independent variable is the different of bleaches, to ensure the accuracy of the experiment, same molarity of sodium thiosulphate solution should be used through the whole experiment. | Solution is taken from the same cup of solution provided. | Volume of bleaches used for dilution (10cm3) | For a fair experiment result, the volume of bleaches used for dilution should be the same for the diluted solutions are in the same concentration. | Using the same pipette to pipette the two solutions and read the pipette reading accurately. | Volume of two bleaches diluted to (100cm3) | The volume of two bleaching solutions diluted into should be the same as to let the concentration of both diluted solutions are same. Differences of the

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