Bromine bromide

Worked Example 7.5 Write a cell schematic for a cell comprising the couples Br2,Br and H+, H2. The bromine bromide couple is the more positive. Assume that all solutions are aqueous. 

SAQ 7.11 Write down an expression for the electrode potential of the bromine bromide couple. [Hint it might help to write the balanced redox reaction first.]... 

Excellent recoveries of bromine (bromide) were obtained on soil samples by this procedure (Table 12.3). 

Following chemical reactions. We will now consider following chemical reactions, which are also called coupled chemical reactions or EC reactions. We will illustrate such a situation with the bromine-bromide couple. 

Appendix 2), so the bromine-bromide couple is fully reversible, and therefore the two peaks - anodic and cathodic - are positioned at an equal distance either side of 1.09 V (see Table 6.3). The forward peak represents the electrode reaction, 2Br -> Br2 + 2e , while the reverse peak represents the reverse electrode reaction, Br2-f-2e" 2Br. We recall that the CV peak height is... 

So we have two currents with the RRDE, where each relates to a concentration the disc current Ip relates to how much analyte is formed (via Faraday s laws), while the ring current I/j relates to how much analyte is reconverted back into starting material (again via Faraday s laws). If we take the example of the bromine-bromide couple, if Ip relates to the formation of bromine from bromide, then I/j relates to the back reaction to reform bromide ion. 

Water samples Bromine Bromide/bromate Ion exchange/isotopic dilution 6jug I"1 bromide 30/tg I"1 bromate Diemer and Heumann (1997)... 

Shimoishi and Toei [766] have described a gas chromatographic determination of selenium in non saline waters based on l,2-diamino-3,5-dibromobenzene with an extraction procedure that is specific for selenium (IV). Total selenium is determined by treatment of non saline water with titanium trichloride and with a bromine-bromide redox buffer to convert selenide, elemental selenium and selenate to selenious acid. After reaction, the 4,6-dibromopiazselenol formed from as little as lng of selenium can be extracted quantitatively into 1 ml of toluene from 500ml of natural water up to 2ng L 1 of selenium(IV) and total selenium can be determined. The percentage of selenium(IV) in the total selenium in river water varies from 35 to 70%. 

Halogen electrodes in molten salts are being used especially for the study of molten halides. In 1930 Hildebrand and Salstrom [98-100] were the first who applied a chlorine reference electrode in molten salts. Up to the present, other authors used and improved this electrode [101-105], The reversible bromine/ bromide electrode was set up for the first time by Hildebrand and Salstrom [98] and improved by Murgulescu et al. [106,107], In the following an example is shown of how to obtain and use a reversible gas electrode in molten salts for the determination of thermodynamic activity. 

Bromine-Bromide Solution Add 1 mL of bromine to 300 mL of glacial acetic acid saturated with dry potassium iodide (about 5 g). Fifteen mL of this solution requires about 40 mL of 0.05 N sodium thiosulfate. Store in a brown bottle in a dark place, and standardize at least once a day during use. 

An example of the reversal of an electron reaction involving an oxidation-reduction pair is the bromine-bromide ion pair ... 

Thus in one of these two oxidation-reduction reactions the bromine-bromide ion electron reaction proceeds in one direction, and in the other reaction it proceeds in the other direction. 

EXAMPLE 15-1 Consider the titration of arsenic(III) with bromate. In a hydrochloric add solution containing excess bromide, the end point can be determined potentiometrically by using the bromine-bromide couple as the potential-determining system. Alternatively, the same titration can be followed amperometrically by measuring the diffusion-controlled current due to excess bromine slightly beyond the end point. At an initial concentration of 5 x 10 M arsenic(III), the potentiometric titration can barely be carried out, because several minutes are required for electrode equilibrium at each point of the titration. The amperometric method gives a successM end point even at 5 x 10 M arsenic(III), the whole titration taking only a few minutes. ////... 

A sensitive gas-chromatographic determination of selenium is possible as 5-chlor-or 5-nitro-piazselenol. These compounds are extractable into benzene or toluene for direct injection into a gas-chromatograph with BCD or TCD After treatment of steel samples with diluted mixtures of equal volumes of hydrochloric and nitric acids in the presence of perchloric acid, the selenium is completely converted into the quadrivalent state. Large amounts of Fe(III) are masked with phosphoric acid. In pure sulfuric acid ultramicro amounts of selenium are converted into seleneous acid with a bromine-bromide redox buffer solution For high-purity... 

S.E. Lorimer, A mathematical model of the current—Potential characteristics for the bromine/bromide ion electrochemical system, Masters thesis, Department of Chemical Engineering, Texas A M University, College Station, TX, 1982. 

The ICP scan data is presented to indicate certain metals reactivity towards acidic bromine/bromide. The acidic bromine leach was carried out to determine the dissolution of impurity elements and to provide a competitive environment for gold loading onto the adsorbents. 

Shapovalov has reported the results of a study of the effects of continuous exposure to elemental bromine, bromides, and methyl bromide on the functions of liver and thyroid gland, and on haematological change, in 140 workers. Spectrophotometric methods have been used to obtain the rate law and other parameters at 298.2 K for Br2 HCN BrCN + H Br. Sill has discussed the... 

Tribromophenol is easily prepared by adding bromine water to an aqueous solution of phenol until the former is no longer decolorized. An excess of bromine gives tribromophenol-bromine (for its preparation see Kohn and Sussmann458), which readily gives up one Br+ and thus functions as a brominat-ing agent. It liberates iodine from iodide,459 so that tribromophenol is formed, with consumption of 6 atoms of Br per mole of phenol, when phenol is titrated with bromine (bromide-bromate), KI, and thiosulfate. 

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