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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:
Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na + ) and iodide anions (I − ) in a crystal lattice .
An iodide ion is the ion I −. [2] Compounds with iodine in formal oxidation state −1 are called iodides.In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate.
Most metal iodides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular iodides, as do metals in high oxidation states from +3 and above. Both ionic and covalent iodides are known for metals in oxidation state +3 (e.g. scandium iodide is mostly ionic, but aluminium iodide is not).
• The -1 oxidation state, hydrogen iodide, is not an oxide, but it is included in this table for completeness. The periodates include two variants: metaperiodate IO − 4 and orthoperiodate IO 5− 6.
The determination of arsenic(V) compounds is the reverse of the standardization of iodine solution with sodium arsenite, where a known and excess amount of iodide is added to the sample: As 2 O 5 + 4 H + + 4 I − ⇌ As 2 O 3 + 2 I 2 + 2 H 2 O
Most alternatives to oxidation with hypervalent iodine reagents require the use of environmentally unfriendly metals. However, they may provide comparable or better yields than hypervalent iodine methods. [14] (12) Exposure of phenols to Fremy's salt or cerium(IV) ammonium nitrate also yields quinones. [15] (13)
Iodate is one of several oxyanions of iodine, and has an oxidation number of +5. It participates in several redox reactions, such as the iodine clock reaction. Iodate shows no tendency to disproportionate to periodate and iodide, in contrast to the situation for chlorate. Iodate is reduced by sulfite: [1] 6HSO − 3 + 2IO − 3 → 2I − ...