page_title: Zinc oxide
section_title: Chemical properties
hierarchical_section_title: Zinc oxide / Chemical properties
caption_attribution_description: Deutsch: Hopeit English: Hopeite. Mineral collection of Bringham Young University Department of Geology, Provo, Utah. Photograph by Andrew Silver. BYU index 9-3077b.
context_page_description: Zinc oxide is an inorganic compound with the formula ZnO. ZnO is a white powder that is insoluble in water. It is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement, lubricants, paints, ointments, adhesives, sealants, pigments, foods, batteries, ferrites, fire retardants, and first-aid tapes. Although it occurs naturally as the mineral zincite, most zinc oxide is produced synthetically.
  ZnO is a wide-band gap semiconductor of the II-VI semiconductor group. The native doping of the semiconductor due to oxygen vacancies or zinc interstitials is n-type. Other favorable properties include good transparency, high electron mobility, wide band gap, and strong room-temperature luminescence. Those properties are valuable in emerging applications for: transparent electrodes in liquid crystal displays, energy-saving or heat-protecting windows, and electronics as thin-film transistors and light-emitting diodes.
context_section_description: Pure ZnO is a white powder, but in nature it occurs as the rare mineral zincite, which usually contains manganese and other impurities that confer a yellow to red color.
  Crystalline zinc oxide is thermochromic, changing from white to yellow when heated in air and reverting to white on cooling. This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn₁₊ₓO, where at 800 °C, x = 0.00007.
  Zinc oxide is an amphoteric oxide. It is nearly insoluble in water, but it will dissolve in most acids, such as hydrochloric acid:
  ZnO  +  2 HCl   →   ZnCl₂  +  H₂O
  Solid zinc oxide will also dissolve in alkalis to give soluble zincates:
  ZnO  +  2 NaOH  +  H₂O   →   Na₂[Zn(OH)₄]
  ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate. ZnO forms cement-like products when mixed with a strong aqueous solution of zinc chloride and these are best described as zinc hydroxy chlorides. This cement was used in dentistry.
  ZnO also forms cement-like material when treated with phosphoric acid; related materials are used in dentistry. A major component of zinc phosphate cement produced by this reaction is hopeite, Zn₃(PO₄)₂·4H₂O.
  ZnO decomposes into zinc vapor and oxygen at around 1975 °C with a standard oxygen pressure. In a carbothermic reaction, heating with carbon converts the oxide into zinc vapor at a much lower temperature (around 950 °C).
  ZnO  +  C   →   Zn(Vapor)  +  CO
caption: Hopeite
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