Introducilon Hypochlorous acid (HClO) is one of the important chlorine oxoacids (Ebbing Gammon, Section 21.9). Solutions

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Introducilon Hypochlorous Acid Hclo Is One Of The Important Chlorine Oxoacids Ebbing Gammon Section 21 9 Solutions 1 (154.8 KiB) Viewed 56 times

Introducilon Hypochlorous acid (HClO) is one of the important chlorine oxoacids (Ebbing Gammon, Section 21.9). Solutions of sodium hypochlorite ( NaOCl), a salt of that acid, are sold as laundry bleach. The hypochlorite anion (ClO) is a strong oxidizing agent, but not as strong as ClO2​,ClO3​, and ClO4​ Purpose In this experiment, you will use an oxidation-reduction titration to determine the quantity of NaOCl in a commercial bleach. Concept of the Experiment As you will see, you can determine the quantity of the ClO−ion in a solution through two oxidationreduction reactions. First, a known quantity of this anion is reduced to Cl ions in an acidic solution, using excess potassium iodide. The I ions are oxidized to I2​ in this reaction. The solution that results is brown because that is the color of I2​ in water. Second, the I2​ is reduced to 1 during a titration with asolution of sodium thiosulfate. Thiosulfate anions (S2​O3​2) are oxidized to tetrathionate ions (S4​O6​2) in this reaction. You may have found this description somewhat confusing, but it should become clear after you have balanced the equations for the two oxidation-reduction reactions in the Prelaboratory Assignment. Moreover, the relationship between the original quantity of ClO ions and the quantity of S2​O32−​ ions used in the titration will be evident after these equations are balanced. Although you could use the disappearance of the color due to aqueous I2​ to detect the endpoint of the titration, this technique would not be very sensitive. Instead, you will use starch as an indicator. Starch reacts with I2​ to form a dark blue color. This reaction is reversible, Consequently, the blue color fades during the course of the titration as I2​ is consumed. The endpoint occurs when one drop of the Na2​ S2​O˙3​ solution causes the color to change from blue to colorless. A trial titration will enable you to locate the endpoints of subsequent titrations more easily.
Experiment 218 412 3. Exact tirrations Trial 23 4 Volume of diluted bleach used (mL) Final buret reading (mL) 10 1010 10 Initial buret reading (mL) 6.6 7.165 7 Volume of 0.0250MNa2​ S2​O3​( mL) 0.10.2 0.1 0.2 Molēs of Na2​ S2​O3​ 656,9 Moles of NaOCl .1625.1725.1512.17 0325325​+345+3025×31 Molarity of NaOCl in diluted bleach (M)+43 03025 +634 Mean molarity (M) 0,03 Calculations:
a. Calculate the molarity of the undiluted bleach solution. b. Commercial bleaches such as Clorox are said to contain 5.25%NaOCl by weight. Is this correct? Use your results and a density of 1.0 g/mL for the bleach in your calculations. These calculations should reflect the precision of the assumed density.