Formation from zinc oxide

Does this type of reaction look familiar You learned in Chapter 6 that this is classified as a synthesis reaction. You also know that early chemists called it an oxidation reaction because oxygen is a reactant. The formation of zinc oxide falls into another, broader class of reactions characterized by the transfer of electrons from one atom or ion to another. This type of reaction is called an oxidation-reduction reaction, commonly known as a redox reaction. Many important chemical reactions are redox reactions. Formation of rust is one example combustion of fuels is another. In each redox reaction, one element loses electrons, and another element takes them. 

In the formation of zinc oxide, the zinc atom loses two electrons during the reaction, becoming a zinc Ion. Its oxidation number Increases from zero to 2+. The oxygen atom gains the two electrons from zinc, becoming an oxide ion. 

Figure 4 The synthesis of porous MOFs directly from a metal oxide using the mechanochemical ILAG technique (a) the rapid (less than an hour) and quantitative synthesis of pillared MOFs enabled and directed by catalytic (about 100-1000 ppm) addition of nitrate or sulfate salts and (b) the quantitative formation of porous ZIFs from zinc oxide by grinding with two equivalents of 2-ethylimidazole. Analogous reactivity with 2-methylimidazole produced the popular material ZIF-8 and, with plain Him, several other open- and close-packed ZIF topologies...

The three stages of thiol film formation on zinc oxide according to Hedberg et al. (From Leidheiser Jr., H., Corrosion Control by Organic Coatings, NACE, Houston, TX, p. S7,1981.)... 

Anhydrous zinc chloride can be made from the reaction of the metal with chlorine or hydrogen chloride. It is usually made commercially by the reaction of aqueous hydrochloric acid with scrap zinc materials or roasted ore, ie, cmde zinc oxide. The solution is purified in various ways depending upon the impurities present. For example, iron and manganese precipitate after partial neutralization with zinc oxide or other alkah and oxidation with chlorine or sodium hypochlorite. Heavy metals are removed with zinc powder. The solution is concentrated by boiling, and hydrochloric acid is added to prevent the formation of basic chlorides. Zinc chloride is usually sold as a 47.4 wt % (sp gr 1.53) solution, but is also produced in soHd form by further evaporation until, upon cooling, an almost anhydrous salt crystallizes. The soHd is sometimes sold in fused form. 

Steam reforming is the reaction of steam with hydrocarbons to make town gas or hydrogen. The first stage is at 700 to 830°C (1,292 to 1,532°F) and 15-40 atm (221 to 588 psih A representative catalyst composition contains 13 percent Ni supported on Ot-alumina with 0.3 percent potassium oxide to minimize carbon formation. The catalyst is poisoned by sulfur. A subsequent shift reaction converts CO to CO9 and more H2, at 190 to 260°C (374 to 500°F) with copper metal on a support of zinc oxide which protects the catalyst from poisoning by traces of sulfur. 

C04-0103. Write the balanced redox reactions for the formation of each of the following oxides from the reaction of molecular oxygen with pure metal (a) chromium(VI) oxide (b) zinc oxide (c) copper(I) oxide. 

Komrska Satava (1970) showed that these accounts apply only to the reaction between pure zinc oxide and phosphoric acid. They found that the setting reaction was profoundly modified by the presence of aluminium ions. Crystallite formation was inhibited and the cement set to an amorphous mass. Only later (7 to 14 days) did XRD analysis reveal that the mass had crystallized directly to hopeite. Servais Cartz (1971) and Cartz, Servais Rossi (1972) confirmed the importance of aluminium. In its absence they found that the reaction produced a mass of hopeite crystallites with little mechanical strength. In its presence an amorphous matrix was formed. The amorphous matrix was stable, it did not crystallize in the bulk and hopeite crystals only grew from its surface under moist conditions. Thus, the picture grew of a surface matrix with some tendency for surface crystallization. 

Experimental results clearly demonstrate that catalytic reaction of dehydration of alcohols on zinc oxide proceeds via formation of radicals. Emission of hydrogen atoms from the catalyzer surface may be associated with structure relaxation of the catalyzer surface excited during the reaction [26]. 

We heated the substrate of zinc oxide containing 10 cm 2 of silver atoms (in this case there was already no emission after completion of deposition) at 300 C. Such thermal treatment results in formation of microcrystals, rather than evaporation adatoms on the surface of the substrate made of zinc oxide. In paper [34] it was shown that microcrystals with diameter 100 A deposited on the zinc oxide surface are acceptors of electrons, therefore the formation of microcrystals results in increase of resistivity of a sensor substrate above the initial value (prior to silver deposition). In this case the initial value of the resistance of sensor-substrate was 2.1 MOhm, after adsorption of silver atoms it became 700 kOhm, and as a result of heating at 300°C and formation of microcrystals - acceptors of electrons it in increased up to 12 MOhm. If such a substrate is subject to deposition of 3-10 5 cjjj-2 silver again, then emission of silver atoms gets detected. From the change of resistivity of sensor-detector due to deposition of silver atoms one can conclude that in this case the emission of atoms is 4 times as low than in experiment with pure substrate made of zinc oxide, which confirms the supposition made on the mechanism of emission of adatoms. 

The presence of zinc with bidentate nitrogen donor ligands in the formation of novel composite materials by hydrothermal reactions has been studied. A zinc-containing one-dimensional material, [Zn(phenanthroline)Mo04] was isolated from molybdate, and from vanadium oxide in the presence of zinc 2,2 -bipyridine [Zn(2,2,-bipyridine)2V40i2] was obtained.212,213... 

The principles needed to design a polymer of low flammability are reasonably well understood and have been systematized by Van Krevelen (5). A number of methods have been found for modifying the structure of an inherently flammable polymer to make it respond better to conventional flame retardant systems. For example, extensive work by Pearce et al. at Polytechnic (38, 39) has demonstrated that incorporation of certain ring systems such as phthalide or fluorenone structures into a polymer can greatly increase char and thus flame resistance. Pearce, et al. also showed that increased char formation from polystyrene could be achieved by the introduction of chloromethyl groups on the aromatic rings, along with the addition of antimony oxide or zinc oxide to provide a latent Friedel-Crafts catalyst. 

---