Chem lab 5 - Once the solution turned pale yellow, starch...

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Sodium Hypochlorite in Bleach by Alex Wittenberg Lab Instructor: Saba Khan October 16, 2009
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Results and Discussion: The purpose of the experiment was to determine the molarity of hypochlorite ion in commercially available bleach (Clorox). Commercially available bleach is made by the following procedure: Cl 2 ( g ) + 2 NaOH ( aq ) ® NaOCl ( aq ) + NaCl ( aq ) + H 2 O ( l ) A diluted bleach solution was created and mixed with a solution containing an excess of iodide ion, I - . The net ionic equation is: OCl - ( aq ) + 2 I - ( aq ) + 2 H 3 O + ( aq ) ® I 2 ( aq ) + Cl - ( aq ) + 3 H 2 O ( l ) The amount of iodine produced was measured by titrating the iodine with a standardized solution of thiosulfate ion, S 2 O 3 2- . The oxidation- reduction reduction is as follows: I 2 ( aq ) + S 2 O 3 2- ( aq ) ® 2 I - ( aq ) + S 4 O 6 2- ( aq ) brown colorless colorless colorless When the distilled water, KI solution, diluted bleach solution, and HCl solution were mixed together, the solution turned dark brown. As the thiosulfate solution was added, the solution became lighter in color.
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Unformatted text preview: Once the solution turned pale yellow, starch was added to the solution. The starch combined with the small amount of iodine remaining in the solution and turns the solution dark blue in color. More thiosulfate was added until the solution became clear. Initial buret volume (mL) Final buret volume (mL0 Difference between final and initial readings (mL) Average difference (mL) 0.3 11.5 11.2 13.3 11.5 26.2 14.7 26.2 40.3 14.1 The molarity of the thiosulfate solution was 0.1013M. It was given in the lab. # molesS 2 O 3 2-( aq ) = (0.0133 L )(0.1013 M ) = 0.00135 moles 0.00135 molesS 2 O 3 2-( aq ) x 1 molI 2 2 molS 2 O 3 2-x 1 molOCl-1 molI 2 x 1 10 mL titrand x 100 mL dil 10 mL x 1000 mL 1 L = 0.675 MOCl-Conclusion : The molarity of the hypochlorite ion in commercially available bleach (Clorox) was determined to be 0.675M....
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This note was uploaded on 10/29/2009 for the course CHEM 2070 taught by Professor Chirik,p during the Fall '05 term at Cornell University (Engineering School).

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Chem lab 5 - Once the solution turned pale yellow, starch...

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