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This clock reaction uses sodium, potassium or ammonium persulfate to oxidize iodide ions to iodine. Sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color. Iodine is generated: 2 I − + S 2 O 2− 8 → I 2 + 2 SO 2− 4. And is then removed:
The relevant reaction is akin to the iodine reaction: thiosulfate reduces the hypochlorite (the active ingredient in bleach) and in so doing becomes oxidized to sulfate. The complete reaction is: 4 NaClO + Na 2 S 2 O 3 + 2 NaOH → 4 NaCl + 2 Na 2 SO 4 + H 2 O. Similarly, sodium thiosulfate reacts with bromine, removing the free bromine from ...
Note that iodometry involves indirect titration of iodine liberated by reaction with the analyte, whereas iodimetry involves direct titration using iodine as the titrant. Redox titration using sodium thiosulphate , Na 2 S 2 O 3 (usually) as a reducing agent is known as iodometric titration since it is used specifically to titrate iodine.
Thiosulfate (IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula S 2 O 2− 3.Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, such as sodium thiosulfate Na 2 S 2 O 3 and ammonium thiosulfate (NH 4) 2 S 2 O 3.
The amount of dissolved oxygen is directly proportional to the titration of iodine with a thiosulfate solution. [1] Today, the method is effectively used as its colorimetric modification, where the trivalent manganese produced on acidifying the brown suspension is directly reacted with ethylenediaminetetraacetic acid to give a pink color. [ 2 ]
Sodium tetrathionate is formed by the oxidation of sodium thiosulfate (Na 2 S 2 O 3), e.g. by the action of iodine: [1] 2 Na 2 S 2 O 3 + I 2 → Na 2 S 4 O 6 + 2 NaI. The reaction is signaled by the decoloration of iodine. This reaction is the basis of iodometric titrations. Other methods include the coupling of sodium bisulfite with disulfur ...
The cut surface of an apple stained with iodine, indicating a starch level of 4–5. The iodine–starch test is a chemical reaction that is used to test for the presence of starch or for iodine. The combination of starch and iodine is intensely blue-black. [1] [2] The interaction between starch and the triiodide anion (I − 3) is the basis ...
Aliphatic hypoiodites can be synthesized through a variant on the Williamson ether synthesis: an alkoxide reacts with iodine monochloride, releasing the alkyl hypoiodite and chloride. [11] Alternatively, the Meyer-Hartmann reaction applies: a silver alkoxide reacts with elemental iodine to give the hypoiodite and silver iodide.