Zinc sulfide reaction with oxygen

Calculate the standard enthalpy change for the reaction of zinc sulfide with oxygen to produce zinc oxide ... 

Ozone, O3, is produced in the laboratory in an instrument called an ozonator, in which an arc discharge generates 3 % ozone in a dry oxygen stream. The gas mixture is passed through a solution of the alkene in methanol or dichloromethane. The first isolable intermediate is a species called an ozonide, which is reduced directly in a subsequent step by exposure to zinc in acetic acid or by reaction with dimethyl sulfide. The net result of the ozonolysis-reduction sequence is the cleavage of the molecule at the carbon-carbon double bond oxygen becomes attached to each of the carbons that had originally been doubly bonded. 

Carbon-carbon coupling of radicals observed in the photo-Kolbe reaction could also be observed with other surface generated radicals. Kisch and coworkers have shown, for example, that cyclic allylic ethers undergo alpha deprotonation under photoelectrochemical activation, producing radicals that can be oxygenated, Eq. (29). On colloidal zinc sulfide, hydrogen evolution accompanies the photocatalytic... 

The primaiy role of sulfur species in the tribochemical processes is passivation by sulfur species on nascent surfaces caused by a severe wear process (extreme pressure conditions) Fe2+ + S2" - FeS, the heat of formation AHf (FeS) = -1.04 eV. The sulfide can prevent adhesion and also the attack of oxygen species, AHf (FeO) = - 2.82 eV (Mori, 1995). There is enough sulfur in engine oil to initiate acid-base reactions in the formation of zinc sulfide (Martin, 1999). Organic sulfur species other than in thiophosphate form can react with the ZnO produced by the phosphate reactions according to the following ZnO + S2 - ZnS + O2. The zinc sulfide can also be directly produced if the polyphosphate contains sulfur atoms in the polymer chain (thiophosphate), for example ... 

The second step (eq. 4.5) is a thermal oxidative process. This initiates the reaction of ZDDP with oxygen, and enhances the decomposition. Since oxygen and/or hydroperoxide is present in the oil, decomposition is not a pure thermal degradation. The main products on the surface are zinc polyphosphates with minor amounts of zinc sulfides. As the rubbing continues, the polyphosphate layer comes into closer contact with water in oil and is hydrolyzed to give short-chain polyphosphates (eq. 4.6). 

Ignition or explosive reaction with metals (e.g., aluminum, antimony powder, bismuth powder, brass, calcium powder, copper, germanium, iron, manganese, potassium, tin, vanadium powder). Reaction with some metals requires moist CI2 or heat. Ignites with diethyl zinc (on contact), polyisobutylene (at 130°), metal acetylides, metal carbides, metal hydrides (e.g., potassium hydride, sodium hydride, copper hydride), metal phosphides (e.g., copper(II) phosphide), methane + oxygen, hydrazine, hydroxylamine, calcium nitride, nonmetals (e.g., boron, active carbon, silicon, phosphoms), nonmetal hydrides (e.g., arsine, phosphine, silane), steel (above 200° or as low as 50° when impurities are present), sulfides (e.g., arsenic disulfide, boron trisulfide, mercuric sulfide), trialkyl boranes. 

Zinc reacts with sulfur in a strongly exothermic reaction to form zinc sulfide and with oxygen to give zinc oxide the latter is yellow when hot but becomes white on cooling (tbermochromism). 

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