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Analysis of Chlorine in Commercial Bleaching Solutions

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Experiment 6 (28-11-08) Analysis of Chlorine in Commercial Bleaching Solutions Objective To determine the molarities of sodium chlorate (I) in two brands of bleach solution by titration. Theory Reaction between chlorate (I) and iodide ions with the present of sulphuric acid: CIO- (aq) + 2I- (aq) + 2H+ (aq) � Cl- (aq) + I2 (aq) + H2O(l) Reaction between hypochlorite ions and iodine: 2S2O32- (aq) + I2 (aq) � 2I- (aq) + S4O62- (aq) Procedures a. Determine the total volume of bleach in the commercial bottles provided. b. Note the price of the sample. c. Wash a 25.0 cm3 pipette with distilled water and then with the bleach solution. d. Pipette 25.0 cm3 of the bleach into a 250.0 cm3 of volumetric flask. e. Make up to the graduated mark of the volumetric flask. f. Stopper the flask and invert it several times in order to mix the contents well. ...read more.


2840 600 Price ($) 20 7.20 Brand Name of bleach : Clorox vs 0.1M Na2S2O3 1 2 3 Final burette reading (cm3) 4.60 8.70 2.20 Initial burette reading (cm3) 43.60 47.60 40.90 Volume of Na2S2O3 added (cm3) 39.00 38.90 38.70 Mean volume = () / 3 = 38.87 cm3 Brand Name of bleach : Kao vs 0.1M Na2S2O3 1 2 3 Final burette reading (cm3) 10.00 1.40 25.30 Initial burette reading (cm3) 33.80 25.30 49.00 Volume of Na2S2O3 added (cm3) 23.80 23.90 23.70 Mean volume = () / 3 = 23.80 cm3 Calculations Clorox No. of mole of S2O32- = = 3.89 x 10-3 mol By equation, no of moles of S2O32- : I2 = 2 : 1 ? no. of moles of I2 liberated = = 1.944 x 10-3 mol By equation, no of moles of I2 : CIO- = 1 : 1 ? no. of moles of CIO- = 1.944 x 10-3 mol No. ...read more.


It loses its function. Suggestion for the improvement - Keep the bleach solution away from sunlight. - Start titration immediately after adding potassium iodide solution and sulphuric acid into the diluted bleach solution. - Starch solution should be freshly prepared before used. Question 1. Clorox is the 'best' buy as it is relatively cheaper than Kao for 1 mole of sodium chlorate (I), which is the basis of commercial bleaches. 2. Sulphuric acid is used to provide hydrogen ions for the reaction between chlorate (I) and iodide ions. 3. First, when bleaching solution is put under sunlight, CIO- ions may be decomposed into chloride ions and oxygen gas. 2CIO- (aq) � 2CI- (aq) + O2 (g) Second, bleaching solution may react with carbon dioxide in air. Chlorate (I) ions in bleaching solution can react with carbon dioxide in air to form carbonate, water and chlorine gas. 2ClO-(aq) + CO2(g) � CO32-(aq) + H2O(l) + Cl2(g) Practical Report (Experiment 6) F.6A Angel Chan (4) Page 1 of 4 ...read more.

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