Vanadium zero ionic strength

There are less data available for the stability constant of V2(OH)2 than were available for those of the monomeric vanadium(III) hydrolysis species, but nevertheless, the majority of the data still come from the work of Pajdowski and co-workers (see Table 11.4). As was the case with V(OH)2, the data have been acquired in chloride media across the temperature range of 20-25 0. It is believed that utilisation of these data without correction will not significantly impact calculations for obtaining the stability constant at zero ionic strength since the change in each constant is likely to be within the uncertainty assigned to each constant. 

The determination of the maj ority of the stability constants for the vanadium( V) hydrolysis species has not been related to reaction (2.5) (M = V02 ). This is because other reactions better facilitate the calculation of the relevant stability constants at zero ionic strength, as is illustrated in the following. For consistency with data given for other cations. Table 11.9 contains the stability constants for all vanadium(V) species that relate to reaction (2.5) (M=V02" ). To undertake these calculations, the derived stability constants at zero ionic strength have been combined with the relevant stability constant of a monomeric vanadium) V) species (also given in the following) and that for water, as given in Chapter 5. 

Three decameric vanadium( ) species have reported stability constants. The formation of the first ofthese species, ( 02)2q(OH)j, has been described using reaction (2.5) M=V02, p= 10, q= 14). The stability constants reported for the formation of ( 02)20(011)24 according to reaction (2.5) have been utilised, with the extended specific ion interaction theory, to determine the stability constant at zero ionic strength and the associated ion interaction coefficients. The variation of the stability constants as a function of ionic strength is illustrated in Figure 11.19. The zero ionic strength stability constant and ion interaction coefficients obtained are... 

The stability and solubility constants derived at 25 °C for zero ionic strength have been used to create a predominance speciation diagram for vanadium(V). The diagram is illustrated in Figure 11.22. The diagram shows that both monomeric and polymeric species have regions of predominance. It is clear from the diagram... 

Vanadium (V) oxidation of o-arabinose and o-xylose in the presence of Mn(II) is first order in Mn(ll) but for sugars and H+, the order is variable, being first order at low concentrations and zero order at high concentrations. The rates increased with the ionic strength. 

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