Acid and Base Data on Binary Oxides

Si02 — ZnO. Incorporation of transition metal ions into MgO increases base sites. The relation between the amount of base sites on metal cation-added MgO and ionic radii of the metal cations is shown in Fig. 3.45. Increase in base amount is prominent as the ionic radii of the metal cations are close to that of Mg. Metal ions whose ionic radii are close to that of Mg easily replace Mg in the MgO lattice. The replacement results in a deformed lattice and unbalanced electron charge distribution, increasing the basicity. 

Factors Determining Acid and Base Sites Generation a. Composition 

For a certain combinations of metal oxide, the number of acid and base sites generated usually depends upon the composition of the binary oxide. Examples are shown in Fig. 3.46 for acid site generation of Si02 MoOs, and Fig. 3.47 for base site 

In coprecipitation, the type of precipitation reagent used also affects the acidic properties of the resulting binary oxide. An example is shown in Fig. 3.49 for Ti(32 - ZnO. One Ti02 — ZnO is prepared using urea as the precipitation reagent while another is prepared using aqueous ammonia. As urea is heated, it decomposes into ammonia and carbon dioxide  

Ammonia dissolves into the solution and carbon dioxide evolves. As a result, the pH of the solution increases. The pH values at different parts in solution at a certain time 

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