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11 Nov 2019
Using the balanced equations given below, determine the overall molar ratio between aqueous oxygen and thiosulfate. Using the known concentration and added volume of sodium thiosulfate solution along with this molar ratio, it is possible to calculate the amount and concentration of dissolved oxygen in the original sample.
Determination of Dissolved Oxygen. Our determination of dissolved oxygen relies on several coupled reactions. Ultimately, the oxidation of manganese by dissolved oxygen drives oxidation of iodide to iodine, which is titrated using the iodine-reducing agent sodium thiosulfate. The water sample is first treated with a manganese(II) solution and a solution of potassium Mn2+(aq) + 2 OH-(aq) â Mn(OH)2(s) oxygen dissolved in the water oxidizes a portion of the manganese( hydroxide to manganese(ID hydroxide. (Note that dissolved oxygen is the limiting reagent throughout these reactions.) To dissolve the manganese(III) cations back in the water completely, a small amount of sulfuric acid is added--the acid protonates the hydroxides, allowing the freed manganese(I) ions to return to solution. 4 Mn(OH)2(s)-O2(aq) + 2 H20() â 4 Min(OH)3(s) 2 Mn(OH)3(s) + 3 HSO4(aq) â 2 Min'"(aq) + 3 SO42-(ag) + 6 H20() Iodide now enters the picture, as the newly dissolved manganese(II) ions have the ability to oxidize iodide. Dissolved molecular iodine forms, producing a yellow-brown solution. Iodide remaining in solution coordinates to the newly produced iodine, yielding the triiodide ion which turns blue in the presence of dissolved starch. L(aq) + rag) â 13-(aq) Finally, sodium thiosulfate solution is added dropwise to the mixture until all of the triiodide has been reduced back to iodide. At this point, the blue color of the starch-triiodide solution will disappear, leaving a colorless solution.
Using the balanced equations given below, determine the overall molar ratio between aqueous oxygen and thiosulfate. Using the known concentration and added volume of sodium thiosulfate solution along with this molar ratio, it is possible to calculate the amount and concentration of dissolved oxygen in the original sample.
Determination of Dissolved Oxygen. Our determination of dissolved oxygen relies on several coupled reactions. Ultimately, the oxidation of manganese by dissolved oxygen drives oxidation of iodide to iodine, which is titrated using the iodine-reducing agent sodium thiosulfate. The water sample is first treated with a manganese(II) solution and a solution of potassium Mn2+(aq) + 2 OH-(aq) â Mn(OH)2(s) oxygen dissolved in the water oxidizes a portion of the manganese( hydroxide to manganese(ID hydroxide. (Note that dissolved oxygen is the limiting reagent throughout these reactions.) To dissolve the manganese(III) cations back in the water completely, a small amount of sulfuric acid is added--the acid protonates the hydroxides, allowing the freed manganese(I) ions to return to solution. 4 Mn(OH)2(s)-O2(aq) + 2 H20() â 4 Min(OH)3(s) 2 Mn(OH)3(s) + 3 HSO4(aq) â 2 Min'"(aq) + 3 SO42-(ag) + 6 H20() Iodide now enters the picture, as the newly dissolved manganese(II) ions have the ability to oxidize iodide. Dissolved molecular iodine forms, producing a yellow-brown solution. Iodide remaining in solution coordinates to the newly produced iodine, yielding the triiodide ion which turns blue in the presence of dissolved starch. L(aq) + rag) â 13-(aq) Finally, sodium thiosulfate solution is added dropwise to the mixture until all of the triiodide has been reduced back to iodide. At this point, the blue color of the starch-triiodide solution will disappear, leaving a colorless solution.
Tod ThielLv2
13 Jun 2019