STOI 903 Laboratory
City Forensics Laboratory
Section – 028
October 13, 2014
Sanitation Worker Accident
The analysis for Experiment 6: STOI 903 was conducted by Lindsey and I. The analysis was performed at Texas State University – San Marcos in the Chemistry lab. The concentrations used in the experiment were 0.5M of sodium hydroxide and 0.5M of sodium hypochlorite. The concentrations of the solutions found in the dumpster were calculated to be .806 M (both sodium hypochlorite and sodium thiosulfate as well). This was found by taking the 6.0% (by mass) sodium hypochlorite and multiplying it by 1 gram of solution, 1000 mL and 1 mol NaClO. This result was then divided by the result of 100g of solvent, multiplied by 1 mL of solution and 1L which equals 60g NaClO. 60g was then divided by the molar mass of NaClO (74.44) which equals .806 mol NaClO. The same can be done for sodium thiosulfate which results in the same molarity.
The method used for the experiment was continuous variations, also called Job’s Method. The method of continuous variations is a simple technique for determining the stoichiometry of reactants in a reaction. The experiment was then performed by trying 8 different combinations of the reactants while recording the change in temperature to determine which combination created the biggest reaction. In this case, 6.25mL sodium thiosulfate and 18.75mL sodium hypochlorite proved to create the most reaction, resulting in a ratio of 1:3 of sodium thiosulfate to sodium hypochlorite.
After the 8 reactions the highest temperature recorded was 41° C. The potential reaction temperature in the dumpster was calculated to be
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