Redox Titration Of Bleach

Title: Redox Titration of Bleach

Procedure:

Part I. Standardization of the KMnO4 Solution

1. 80 mL of KMnO4 solution were obtained in a clean, dry beaker, along with a 50.00 mL buret.

2. The buret was properly conditioned and the volume of the KMnO4 solution was adjusted below the 0 mL mark.

3. Three 250-Erlenmeyer flasks were rinsed with tap and DI water and labeled #1,#2,#3.

4. Three samples of Fe (NH4)2(SO4)2•6H2O weighing between 0.25 – 0.30 g using a weigh boat were obtained. The balance was tare out with the weighing boat and any excess solid was placed in beaker labeled “waste”. These masses were recorded.

5. Solids were transferred to the flasks for Run #1, #2 , and #3, repectively.

6. Each solid sample of Fe(NH4)2(SO4)2•6H2O was dissolved in 10 mL of DI water. Then with a graduated cylinder, 2mL of 9 M H2SO4 were measured and poured into the flask for Run #1. This process was repeated for the Run #2 and #3. After that, 2 drops of H3PO were added to each of the flasks, and the flasks were swirled to mix solution completely.

7. The magnetic stir bar was put in flask for Run #1, and it was placed on the stir plate. The buret tip was lowered until it was inside the mouth of the flask. Stir plate was turned on and the solution was mixed smoothly.

8. The initial volume of the buret was recorded for Run #1. Slowly the KMnO4 solution was added to the titration flask, making sure it didn’t land on the stir bar. When the pink color began to persist in solution, the titration was slowed down drop by drop. Titration continued until one drop caused the entire solution to remain light pink for at least 30 sec. the final volume of buret was recorded and the total volume for Run #1 was calculated.

9. The resulting solution was poured into a waste beaker to recover the magnetic stir bar using crucible tongs. Stir bar was washed with DI water for the next run.

10. The same process for the titration for Run #1 was repeated for Run #2 and #3. The total volume for all titrations was calculated.

11. Resulting solution were poured into waste beaker, and the Erlenmeyer flasks were rinsed with tap and DI water.

Part II. Determining the Oxidizing Power of Bleach

1. Three Erlenmeyer flasks were labeled #1, #2, and #3.

2. Flask #1 was placed on a balance and the doors were closed. The balance was tare out. The flask was removed to add 8-10 drops of bleach, and then it was put back on balance. The mass of bleach was recorded immediately.

3. 10 mL of DI water were added to the flask containing bleach.

4. Using a 10 mL graduated cylinder, 2.0 mL of 9 M H2SO4 were transferred to this same flask. It was swirled to mix solution completely.

5. The buret was refilled with KMnO4 solution and the initial buret reading was record for flask #1. The titration was carried out using the same process above. The final buret reading was recorded and the total volume for Run #1.

6. The same process was used for Runs #2 and #3.

7. Resulting solutions were poured into a waste beaker. After all titrations were finished the contents of the waste beaker were poured into a labeled wasted container in the fume hood. Erlenmeyer flasks were rinsed with tap and DI water.

Data Table 1: Standardization of the KMnO4 Solution

Run Mass FAS Volume KMnO4 Molarity KMnO4

1 0.2865g 12.80mL 1.426*10-2 M

2 0.2975g 12.20mL 1.562*10-2 M

3 0.2530g 10.60mL 1.529*10-2 M

Average Molarity: 1.506*10-2 M

Data Table 2: Determining the Oxidizing Power of Bleach

Run Mass of Bleach Volume KMnO4 Mass H2O2 Mass % H2O2

1 0.1956g 6.20mL 7.519*10-3 3.844%

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