Titration Analysis of Commercial Bleach
Introduction
In order to determine the percentage of sodium hypochlorite in two different commercial bleaches and compare the relative effectiveness of the two bleaches a titration procedure will be used. Titration is a procedure for determining an unknown concentration of a solute using a reaction with a second solution with a known concentration. Commercial bleaches contain sodium hypochlorite. This is the active ingredient. In experiment 7 we demonstrated the ability to do a titration procedure to determine the sodium hypochlorite percentage in two commercial bleaches. Once we figured the two percentages we compared them to see which was the strongest. To determine the amount of NaClO in each solution we had to perform two successive oxidation reduction reactions. For the experiment to have been successful NaClO(aq)+2NaI(aq)+2HC2H3O2(aq)→I2(aq)+NaCl(aq)+2NaC2H3O2(aq)+H2O(l) needed to become colorless shown as: I2(aq)+2Na2S2O3(aq)→Na2S4O6(aq)+2NaI(aq). Before beginning, we thought the second bleach would be stronger.
Methods and Materials
1. First, we gathered all of the materials, which included: * Buret Clamp * Buret * Ring Stand * Small Funnel * Beaker for collecting waste materials * 125 mL Erlenmeyer flask
2. Then we rinsed the buret with 10 mL of 0.100 M sodium thiosulfate (Na2S2O3), using the small funnel, to clean the buret. The sodium thiosulfate was discarded into the waste beaker.
3. After the cleaning process, we made sure the buret valve was in the closed position. We then filled the buret with 0.100 M Na2S2O3. It is acceptable for the liquid to be over the zero mark at this time.
4. We then placed the waste beaker beneath the buret and opened the valve quickly and watched and listened for an air bubble to leave the tip of the buret. We then quickly turned the valve off. We made sure the liquid was at the zero mark or a few mL below. The experiment is now ready for titration.
5. Next, we placed 50 mL of deionized water in the 125 mL flask and dissolved two grams of sodium iodine (NaI) in the water. Then we added 10 mL of concentrated acetic acid (HC2H3O2) and mixed it thoroughly by swirling.
6. Then 10 mL was poured into one of the bleach samples using a 50 mL beaker. Using a pipet we added 2 mL of the bleach sample into the NaI HC2H3O2 mixture. The mixture turned brown from the diatomic molecular iodine that was created during the reaction.
7. We began titrating the thiosulfate solution into our reaction flask and added 1-2 mL at a time. After adding each addition of the 1-2 mL, we swirled the flask to mix the contents. The brown solution began to lighten, so we added the thiosulfate solution in smaller increments until the solution is a very light brown.
8. Then, we added 2 mL of starch solution and swirled the flask to mix its contents. This turned the solution a dark blue or black color.
9. We resumed titrating the thiosulfate solution one drop at a time swirling the flask until the solution was clear or colorless. This was the end point of our titration process.
10. We prepared another bleach sample by repeating steps 5 and 6
11. After recording the initial volume missing in our data sheets, we titrated the second sample as before in steps 7 through 9. We had to do a third trial because our first two were not within 0.5 mL of each other.
12. We then repeated the sample preparation and titration steps for a second commercial bleach solution.
Results
Sample 1 | Trial 1 | Trial 2 | Trial 3 | Final Buret | 6.10 mL | 13.45 mL | 5.55 mL | Initial Buret | 2.25 mL | 6.10 mL | 0 mL | Volume of thiosulfate | 3.85 mL | 7.35 mL | 5.55 mL | Avg. Volume of Thiosulfate | 5.58 mL | | | % NaClO | .9486% | | |

Sample 2 | Trial 1 | Trial 2 | Trial 3 | Final Buret | 12.50 mL | 19.50 mL | 10 mL | Initial Buret | 0 mL | 12.50 mL | 0 mL | Volume of Thiosulfate | 12.50 mL | 7.00 mL | 10 mL | Avg. Volume of Thiosulfate | 9.83 mL | | | % NaClO | 1.6711% | | |

The percent of NaClO was found by using the formula: 0.170(V)
Discussion
Through titration and redox reactions we were able to discover which bleach was more concentrated. The measured amount of thiosulfate solution used along with its known concentration allowed us to conclude how much iodine reacted. Considering the amount of iodine is directly related to the amount of hypochlorite present in the bleach, the titration with the thiosulfate conclusively told us the quantity of hypochlorite in the bleach. We found the percentage of sodium hypochlorite by using the formula:
% of NaClO= 0.170(v). By using this formula and the data we acquired through the procedure, we discovered that the second bleach’s percentage was higher than the first. This proved our theory that the second bleach would be stronger and harder to dilute.

Conclusion 1. After titrating both NaClO solutions, we successfully proved our hypothesis. 2. We found everything we hoped to find. Redox reactions helped with this. 3. The relevance of this is to determine which bleach would be more efficient. 4. The first solutions concentration was .95% 5. The second solution had a concentration of 1.67% 6. Because of the higher concentration, sample 2 took more mL to dillute.

References 1. Department of Physical Sciences, OCCC. Laboratory for Survey of General, Organic, and Biochemistry. Hayden-McNeil. Plymouth, MI. 2011. 2. Timberlake, Karen C. Chemistry, 11 ed. Prentice Hall. Glenview, IL. 2012.
References
3. Department of Physical Sciences, OCCC. Laboratory for Survey of General, Organic, and Biochemistry. Hayden-McNeil. Plymouth, MI. 2011. 4. Timberlake, Karen C. Chemistry, 11 ed. Prentice Hall. Glenview, IL. 2012.