Reactions metal oxides with water

The oxides of low-valency metals (i.e., with cations in oxidation number < -i-4) are typically ionic compounds [76]. They are most frequently easily obtained in crystalline forms. In ionic metal oxides the coordination of the cations (four to eight) is generally higher than their valency (one to four) and this also occurs for the coordination of 0 oxide ions (three to six). The bulk basic nature of the ionic metal oxides is associated with the strong polarization of the metal-oxygen bond, to its tendency to be dissociated by water and to the basic nature of the products of their reaction with water (i.e., the metal hydroxides) [67]. 

H2S04(aq) + 2NaOH(aq) - Na2S04(aq) + 2H20(P Most metal oxides are bases. Therefore, a metal oxide will react with an acid in a neutralization reaction to form a salt and water. 

The survey of the investigations and results covers the release of water from salts and hydroxides, the calcination of carbonates and oxalates, the reactions of metallic oxides and carbonates with SO2, and reactions on the surface of carbon. The application of the non-isothermal method to the thermal decomposition of carboxylic acids and polymeric plastics as well as to the pyrolyses of natural substances, in particular bituminous coal, is explained. Finally, chemical reactions in a liquid phase, the desorption of gases from solids, annihilation processes in disturbed crystal lattices and the emission of exo-electrons from metallic surfaces are discussed. 

Luminescence Spectra from n-TiCh and n-SrTiCh Semiconductor Electrodes and Those Doped with Transition-Metal Oxides As Related with Intermediates of the Photooxidation Reaction of Water. Mechanistic aspects clarified using photo-and electroluminescence measurements. 407... 

A significant problem in studies on photocatalysis is the definition of positive hole. Positive hole is defined as a defect of an electron (i.e., a positive hole must be included in a substance, while an electron is a real substance). Therefore, not only h produced by photoinduced band-to-band transition in solid materials but also a hydroxyl radical, which is a one-electron deficient hydroxyl anion, can be a positive hole. If this definition is accepted, there should be no difference in the photocatalsrtic oxidation mechanisms between direct hole transfer and surface-adsorbed hydroxyl radical reaction, since it is well known that the surface of a metal oxide is covered with chemically or physically adsorbed water and a positive hole passing through this water layer into a solution may be a hydroxyl radical or its protonated or deprotonated species (Fig. 4). Actually, hydroxyl... 

SAFETY PROFILE A nuisance dust. Moderately toxic by ingestion. An eye irritant. Does not occur freely in nature, but is found as silicon dioxide (silica) and as various silicates. Elemental Si is flammable when exposed to flame or by chemical reacdon with oxidizers. Violent reactions with alkali carbonates, oxidants, (A1 + PbO), Ca, CS2C2, CI2, C0F2, F2, IF5, Mnp3, Rb2C2, FNO, AgF, NaK alloy. When heated it will react with water or steam to produce H2 can react with oxidizing materials. See also various silica entries, SILICATES, and POWDERED METALS. 

Answer (a) Since rubidium is an alkali metal, we would expect Rb20 to be a basic oxide. This is indeed true, as shown by rubidium oxide s reaction with water to form rubidium hydroxide ... 

---