Performed calculations for the standard and theDO content can be seen in the appendix. Conclusions and Recommendations The dissolved oxygen (DO) content ofthe water sample is calculated to be at 2.049ppm and it can be concluded based on theresults of the experiment that the body of waterwhere the sample was taken theoreticallycannot support life because it is highly polluted(See Table 1). Relative standard deviation is at41.595 ppt and its confidence interval at 95% is2.048631741±0.211547453. These results are however deemedanomalous since aquatic life do exist in thesource of the water sample. It is hypothesizedthat the DO content of the sample wassignificantly altered by heterotrophic organismspresent in the sample. The sample was storedfor two days giving these organisms plenty oftime to consume most of its DO content and thusleading to false results. Other than theconsumption of oxygen, the deviation of the DOcontent can be caused by errors such as alteringthe correct order of the addition of reagents,inducing air bubbles during titration, or waterused in the experiment is not boiled. To avoid such anomalous results in thefuture, it is best that the water sample must besubjected to Winkler titration immediately toavoid addition or reduction of DO content. Thetemperature of the sample should also be notedto better compare accepted DO content forwater quality. Series of replications of theexperiment is also recommended to give aprecise data of the actual DO content in thewater source. ReferencesSkoog, Douglas A., Donald M. West, and F. James.Holler. Fundamentals of analytical chemistry. 9thed. Fort Worth: Saunders College Pub., 1996.Print.Petrucci, Ralph H. General chemistry: principlesand modern applications. Toronto, Ont.: PearsonCanada, 2011. Print.
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R. J. C. De Guzman / Chemistry 26.1 (2017) P a g e | 4Soden,JM."TheWinklerTitrationMethod." Sciencing. Leaf Group, n.d. Web. 28Mar. 2017.Fondriest Environmental, Inc. “MeasuringDissolvedOxygen.”FundamentalsofEnvironmental Measurements. 7 Jan. 2014. Web.“Information about end point detection withstarch in iodometric titration.” Iodometrictitration - detection of end point witch starch, 22Mar. 2014, Web. Clemente, Jamela Jirah L. “Redox Titration:Winkler Method for Dissolved Oxygen ContentDetermination.” Diliman, Quezon City, Universityof the Philippines, University of the Philippines,2013.Rivera, R.Y.A. “Quantitative Determination ofDissolved Oxygen Content by Winkler RedoxTitration.” Universityof thePhilippines,University of the Philippines, 2015.Appendix A.Raw Data Table Standardization of Na2S2O3 Solution Primary Standard used: KIO3Formula mass of 1 standard: 214 g/mol%Purity of 1 standard: 99.4Weight of standard, g: 0.15Volume of standard solution: 150 mL Trial123Volume of KIO3 Standard, mL404040Final Volume Na2S2O3, mL37.637.137.6Initial volume Na2S2O30.60.1 0.6Net volume of Na2S2O337.0Average M Na2S2O3 0.0011298307 M Sample Analysis Location of sampling: Science Complex Park, Institute of Mathematics.
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