Cerium half-reactions

The molar concentrations of Ce(IlI), Ce(lV), and Fe(III) are easily computed at this point, but that for Fe(Il) is not. Therefore, Esystem computations based on the cerium half-reaction are more convenient. The concentrations of the two cerium ion species are... 

Write a balanced half-reaction for the reduction of cerium(IV) ions to cerium(III) ions. 

Cerium (IV) solution in 0.1 M H2S04 is an ideal oxidant for many redox titrations. The half-reaction is as follows ... 

The half-reaction of two ions such as Ce and Ce, neither of which can serve as an electrode, is done with an inert electrode such as a platinum bar. Diagram the apparatus for the electrochemical reaction of aqueous cerium(lV) ion and cerium(lll) ion with Mn04 and Mn. (Cerium(lV) ion is a better oxidizing agent than is permanganate ion.)... 

For oxidation-reduction reactions that occur in aqueous solution, it is often useful to separate the reaction into two half-reactions one involving oxidation and the other involving reduction. For example, consider the unbalanced equation for the oxidation-reduction reaction between cerium(IV) ion and tin(II) ion ... 

Ammonium peroxydisulfate, (NH4)2S20h, is also a powerful oxidizing agent. In acidic solution, it converts chromium(lll) to dichromate, cerium(III) to cerium(IV), and manganese(II) to permanganate. The half-reaction is... 

Solutions of permanganate ion and cerium(IV) ion are strong oxidizing reagents whose applications closely parallel one another. Half-reactions for the two are... 

The E° values listed in Table 12.1 are for the case where all species are at an activity of 1 M. However, the potential of a half-reaction may depend on the conditions of the solution. For example, the E° value for Ce + q Ce is 1.61 V. However, we can change this potential by changing the acid used to acidify the solution. (See Table C.5 in Appendix C.) This change in potential happens because the anion of the acid complexes with the cerium, and the concentration of free cerium ion is thereby reduced. 

Some reactions in which one half-reaction is irreversible do occur rapidly. Several oxidizing and reducing agents containing oxygen are reduced or oxidized irreversibly but may be speeded up by addition of an appropriate catalyst. The oxidation of arsenic(ni) by cerium(IV) is slow, but it is catalyzed by a small amount of osmium tetroxide, OSO4. 

Results and Discussion. Of the 12 samples of starch graft copolymer synthesized, half were hydrolyzed to anionic polyelectrolytes. Synthesis data on these 6 samples are given in Table 2. These particular samples were chosen for hydrolysis because the samples can be intercompared to see the effect of synthesis variables on ultimate product properties. Samples 5, 8, and 11 have the same mole ratio of cerium ion to starch backbone, N, in their reaction mixture. Samples 7, 8, and 9 all have the same refctable mass per starch molecule,... 

Catalysis of the decomposition by several metal ions has been reported . The order in peroxomonosulphate was found to be one, except for reaction with cobalt(II) and cerium(IV) (both second-order in the sulphate) and manga-nese(II) (half-order). Formation of a complex with cerium(IV) and peroxomonosulphate has been both asserted and denied . Catalysis by copper(II) is not significant unless manganese is also added, at least in the presence of some hydrogen peroxide ... 

Nikiforidis G, Berlouis L, Hall D, Hodgson D (2013) A study of different carbon composite materials for the negative half-cell reaction of the zinc cerium hybrid redox flow cell. Electrochim Acta 113 412-423. doi 10.1016/j.electacta.2013.09.061... 

The Ce + ion is one of the most active catalysts for peptide hydrolysis. Its activity is much higher than that of the trivalent lanthanide ions and other transition metal ions. In particular, Ce + is far superior to other tetravalent ions like Zr" or Hf +. Yashiro et al. (1994) reported that dipeptides and tripeptides were efficiently hydrolyzed under neutral conditions by the y-cyclodextrin complex of cerium(IV). Komiyama and coworkers (Takarada et al., 2000) studied the catalytic hydrolysis of oligopeptides by cerium(IV) salts. The hydrolysis is fast, especially when the oligopeptides contain no metal-coordinating side-chains. The hydrolysis rates of the dipeptides, tripeptides and tetrapeptides is similar. The hydrolysis reaction was performed at pH 7 and 50 °C and under these conditions, the half-life of the amide bond was only a few hours. The authors found that ammonium hexanitratocerate(IV) is more active than other cerium(IV) compounds like ammonium cerium(IV) sulfate, cerium(IV) sulfate and cerium(IV) hydroxide. The lower reactivity of ammonium cerium(IV) sulfate is ascribed to the competitive inhibition by sulfate ions, while the low reactivity of cerium(IV) sulfate and cerium(IV) hydroxide can be explained by their poor solubility in water. However, in the reaction mixtures at the given reaction conditions, most of the cerium(IV) consists in a gel of cerium(IV) hydroxides. No oxidative cleavage has been observed. 

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