10 mL of bleach with an unknown concentration is added to a 100mL volumetric flask. The...

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Chemistry

10 mL of bleach with an unknown concentration is added to a100mL volumetric flask. The solution is then finished withdeionized water. 10 mL of this diluted bleach solution is thenadded to an erlenmeyer flask along with 1 scoop of KI, and 5 L of2M HCl. This solution is then titrated with Na2S2O3 until it is apale yellow color, then a starch indicator is added and titrationis completed until the solution is clear. If 43 mL of Na2S2O3 wasrequired, what is the percent of sodium hypochlorite in the bleach?How would it be calculated? A step by step answer would be verymuch appreciated.
NaOCL + 2HCl --> NaCl + H2O + Cl2
Cl2 + 2I- --> I2 +2Cl-
2S2O3^2- +I2 --> S4O6^2- +2I-

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4.1 Ratings (648 Votes)

Bleach is compared by the reaction of Cl2 with a base usually a strong one For the most part this base is Sodium Hydroxide NaOH which yields NaClO sometimes written as NaOCl sodium hypochlorite When aqueous NaClO ionizes to Na and ClO Sodium and hypochlorite ions When you bleach something the ClO ion is used in an oxidationreduction change of ionic charge reaction and is reduced to Cl The reducing agent being oxidized is the stain being acted on by the bleach Thus we can easily find the concentration of OCl in a solution by reacting a known mass of solution commonly halide ions for this we will use an Iodine ion in an acidic solution OCl aq 2I aq 2H3O aq I2 aq Cl aq H2O l As the iodine is in excess the reaction of OCl goes to completion Now we must determine the amount of I2 formed by means of titration with Na2S2O3 sodium thiosulfate I2 aq 2S2O32 aq 2I aq S4O62 aq S2O3 2 thiosulfate ion See Answer

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