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30 Oct 2009, 10:39 PM
| #1 (permalink) |
| New Member  HSC: 2009 Gender: Female
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20 Nov 2009, 9:12 PM  | Helpppp You can hide this advertisement by registering. i dont get the winkler method.... can someone please explain.thanks  |
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31 Oct 2009, 3:42 PM
| #2 (permalink) |
| New Member HSC: 2009 Gender: Male
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12 Nov 2009, 9:48 PM | Re: Helpppp In case you don't know, it is not compulsory to know the complicated Winkler method. Instead, you can refer to the electrolysis method in which an 'electrolytic oxygen sensor' is used to determine Dissolved Oxygen. The sensor is placed above the test solution and oxygen diffuses into it. This causes reduction at the cathode in the sensor: (O2)+(4H+)+(4e-)=(2H2O) and oxidation at anode: (Ag)+(Cl-)=(AgCl)+(e-) as there is buffered HCl in the sensor. The conentration of oxygen is proportional to the electric current produced in the sensor. |
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31 Oct 2009, 3:54 PM
| #3 (permalink) |
| ♪웨딩드레스  HSC: 2009 Gender: Male Location: In a box under your bed .
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Yesterday, 9:15 PM | Re: Helpppp The Winkler method involves the reaction of sodium thiosulfate and oxygen gas with manganese and iodide ions as intermediate reactants. o Step 1: Oxygen oxidises Mn2+ (2Mn2+ + O2 + 4OH- → 2MnO(OH)2). o Step 2: The resulting solution is then acidified and iodide ions are added (MnO(OH)2 + 2I- + 4H+ → I2 + Mn2+ + 3H2O) (Iodide is oxidized to iodine). o Step 3: The iodine is then titrated with sodium thiosulfate solution (I2 + 2S2O32- → 2I- + S4O62-). Starch is used as an indicator as it forms a deep blue colour with iodine. The formation of a colourless solution
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