Acid-base behavior of oxides

Periodic Trends Acid-Base Behavior of Oxides movie... 

O Ronald L. Rich, "Periodicity in the Acid-Base Behavior of Oxides and Hydroxides," /. Chem. Educ., Vol. 62,1985,44. 

These atomic properties have a profound effect on many macroscopic properties, including metallic behavior, acid-base behavior of oxides, ionic behavior, and magnetic behavior of the elements and their compounds. 

We can use these principles to explain the acid-base behavior of oxides when they are dissolved in water. For example, when a covalent oxide such as sulfur trioxide is dissolved in water, an acidic solution results because sulfuric acid is formed ... 

Remember, though, that some elements don t lit these categories as graphite, non-metallic carbon is a good electrical conductor the nonmetal iodine is shiny metallic gallium melts in your hand mercury is a liquid and iron is brittle. Despite such exceptions, in this discussion, we U make several generalizations about metallic behavior and its application to the acid-base behavior of oxides. 

Acid-Base Behavior of Oxides Metals are also distinguished from nonmetals by the acid-base behavior of their oxides in water ... 

The pattern of oxidation states correlates with the pattern of acid-base behavior of d-metal oxides. Although most d-metal oxides are basic, the oxides of a given element show a shift toward acidic character with increasing oxidation number, just as the oxoacids do (recall Section 10.10). The family of chromium oxides is a good... 

The pattern of oxidation states accounts for the pattern of acid-base behavior of d-metal oxides. Although most d-metal oxides are basic, the... 

Formic acid is a popular molecule for probing the catalytic properties of metal oxides [23-28], The selectivity of its decomposition has frequently been used as a measure of the acid-base properties of oxides. This is a tempting generalization to make oxides that produce dehydration products (H2O and CO) are described as acidic oxides, while their basic counterparts produce dehydrogenation products (H2 + CO2). It has been shown that in many cases the product selectivity is better connected to the surface redox behavior of the oxide [29], Thus, more reducible surfaces produce higher yields of CO2, Consequently, particular attention has been paid in surface science studies to the interaction between adsorbed formate ions (the primary reaction intermediate) and surface metal cations, as well as to the participation of lattice oxygen anions in the surface reaction mechanism,... 

Most of the recent adsorption literature has emphasized the importance of the acid-base properties of oxide surfaces when explaining or estimating their sorption behavior. However, Sveijensky (1993) has shown that log values for the adsorption of a specific cation by multiple mineral sorbents are a simple linear function of l/e, where e is the dielectric constant of each mineral. He has used this approach to estimate CC and TL model K"" values for the adsorption of up to 18 cations on 7 oxide and silicate mineral surfaces. 

The interpretation of the viscosity-temperature behavior of these complex systems is difficult since many aspects of the melt conditions must be simultaneously considered. These include the chemical composition of the melt to establish the nature of the polymeric network including the amphoteric behavior of species like AI2O3 and Fe2O3> as well as the acid/base behavior of mixed valence constituents such as iron oxides, and the formation of immiscible liquid phases sometimes associated with the existence of several types of stable anions of significantly different size or charge in the system the nature of the container since some of it may dissolve and affect the composition of the melt the existence of a solid phase to establish the effect on the composition of the residual liquid phase (the solid phase may not be the one expected from related phase equilibrium studies) the relative amount of the liquid and solid phases to establish the composition of the liquid phase (this composition changes as the solid crystallizes out of... 

Casamassima, M. et al., Acid-base behavior of aluminum and silicon oxides—a combination of two approaches XPS and Lewis acido-basicity rest potential and Brpnsted acido-basicity, Appl. Surf. Sci., 52, 205, 1991. 

Figure 8.17 The trend in acid-base behavior of eiement oxides. The trend in acid-base behavior for some common oxides of Group 5A(15) and Period 3 elements is shown as a gradation in color (red = acidic blue = basic). Note that the metals form basic oxides and the non-metals form acidic oxides. Aluminum forms an oxide (purple) that can act as an acid or as a base. Thus, as atomic size increases, ionization energy decreases, and oxide basicity increases.

Summarize the acid-base behavior of the main-group metal and nonmetal oxides in water. How does oxide acidity in water change down a group and across a period ... 

To date the acid-base behavior of several hydrous oxide systems, Au,41 Ir,4 Rh,42 Ni,43 and Pt27 has been discussed in considerable detail. It was also suggested recently that, as will be discussed later, anionic species may be involved in the onset of anodic oxidation of metals such as Pt,44 Pd,28 Ni,45 and Au28 where a significant decrease in the initiation or onset potential (RHE scale) for surface oxidation is observed on increasing the solution pH. 

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