Thiosulfate ions

Silver Bromide. Silver bromide, AgBr, is formed by the addition of bromide ions to an aqueous solution of silver nitrate. The light yellow to green-yeUow precipitate is less soluble in ammonia than silver chloride, but it easily dissolves in the presence of other complexing agents, such as thiosulfate ions. 

The thiosulfate ion, 820 is a stmctural analogue of the sulfate ion where one oxygen atom is replaced by one sulfur atom. The two sulfur atoms of thiosulfate thus are not equivalent. Indeed, the unique chemistry of the thiosulfate ion is dominated by the sulfide-like sulfur atom which is responsible for both the reducing properties and complexing abiUties. The abiUty of thiosulfates to dissolve silver haUdes through complex formation is the basis for their commercial appHcation in photography (qv). 

Calculations from binding-force measurements (2) indicate the limiting stmctural forms of the thiosulfate ion ... 

The thiosulfate ion has tetrahedral symmetry and the six fundamental modes are both infrared and Raman active. The calculated frequencies (3) are in good agreement with experimental values (4). 

The low value of the S—S force constant compared to that of S—O is consistent with the ease of cleavage of the S—S bond. Spectral data indicate that the stmcture of the thiosulfate ion in soHd thiosulfates is the same as that of the ion in solution. 

X-ray crystallographic analysis of the sodium thiosulfate pentahydrate [10102-17-7] crystal indicates a tetrahedral stmcture for the thiosulfate ion. The S—S bond distance is 197 pm the S—O bond distance is 148 pm (5). Neutron diffraction of a barium thiosulfate monohydrate [7787-40-8] crystal confirms the tetrahedral stmcture and bond distances for the thiosulfate ion (6). 

Thermodynamic Properties. The heat of formation of the thiosulfate ion, —5.75 kJ/g (—1.37 kcal/g), was determined by studying the equihbrium of the following reaction ... 

Some metal thiosulfates are inherently unstable because of the reducing properties of the thiosulfate ion. Ions such as Fe " and Cu " tend to be reduced to lower oxidation states, whereas mercury or silver, which form sulfides of low solubiUty, tend to decompose to the sulfides. The stabiUty of other metal thiosulfates improves in the presence of excess thiosulfate by virtue of complex thiosulfate formation. 

The thiosulfate ion is a moderately strong reducing agent as indicated by the couple... 

Figure 15.30 Structure of the thiosulfate ion and its various modes of coordination (a) uncoordinated...

Iodine reacts with thiosulfate ion, S 2-, to give iodide ion and the tetrathionate ion, S4062-. 

Below are two different Lewis structures for foe thiosulfate ion (Sjty-). Which is foe better Lewis structure based only on formal charge ... 

Thermal equilibrium, 56 Thermite reaction, 122 Thermometers, 56 Thiosulfate ion, 362 Third-row elements, 101 compounds, 102 physical properties, 102 properties, table, 101 Third row of the periodic table, 364 Thomson, J. J., 244 Thomson model of atom, 244 Thorium... 

Nucleophilic catalysis is also observed with iodide ions. Fluoride ion does not form nitrosyl fluoride under diazotization conditions, as is to be expected from Pearson s hard and soft acids and bases principle which was discussed briefly in Section 3.2. More recently, nucleophilic catalysis has also been shown to occur with thiocyanate ion (SCN ), thiosulfate ion (HS2Of), dimethyl sulfide, and thiourea (H2NCSNH2) or its alkyl derivatives (see below). 

L.21 Thiosulfate ions (S,0,2-) disproportionate in acidic solution to give solid sulfur (S) and hydrogen sulfite ion (HSO ) ... 

Sflf-Test 1S.4A What is the oxidation number of sulfur in (a) the dithionate ion, S2062 (b) the thiosulfate ion, S2032- ... 

Primary and secondary but not tertiary alkyl halides are easily converted to Bunte salts (RSSOj ) by treatment with thiosulfate ion. ° Bunte salts can be hydrolyzed with acids to give the corresponding thiols or converted to disulfides, tetrasulfides,... 

Suspensions of semiconductors with heterojunctions formed by CdS or solid solution ZnyCdi-yS and Cu , S have been prepared and tested as photocatalysts for photochemical hydrogen production [278]. With platinized powders of Zno.nCdo.ssS/CujS in solution containing both S and SOj ions, hydrogen was generated concomitantly with thiosulfate ions with quantum yield of about 0.5. 

Pedraza, A. M. Villegas, I. Freund, P. L. Chornik, B. Electro oxidation of thiosulfate ion on gold. Study by means of cyclic voltammetry and Auger electron spectroscopy. J Electroanal. Chem. Inter. Electrochem. 1988, 250, 443 149. 

The original ion-exchange treatment was developed for competition between reactive and inert monoanions, but Chaimovich, Quina and their coworkers have extended it to competition between mono and dianions (Cuccovia et al., 1982a Abuin el al., 1983a). The ion-exchange constant for exchange between thiosulfate dianion and bromide monoanion is not dimensionless as in (7) but depends on salt concentration, and the formalism was developed for analysing micellar effects upon reaction of dianionic nucleophiles, e.g. thiosulfate ion. 

The value of k /ky, is larger than unity for reaction of thiosulfate ion with n-butyl bromide. There is insufficient evidence to know whether this difference is characteristic of micelle-assisted reactions of dianionic nucleophiles (Cuccovia et al., 1982a). 

The decomposition of thiosulfate ion is promoted in an acidic solution. If the white solid is Na2SOreaction with strong acids such as HC1. By contrast, if the white solid is Na2S203, S02(g) will be liberated and a pale yellow precipitate of S(s,rhombic) will form upon addition of HCl(aq). 

Finally, the triiodide ion is titrated with a known solution of thiosulfate ions, which forms iodide ions ... 

Write a balanced half-reaction that shows the oxidation of thiosulfate ions, 8203 , to sulfite ions, SOs ", in a basic solution. 

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