Zinc oxide

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Zinc oxide
Names
IUPAC name
Zinc oxide
Other names
Amalox
Calamine
Chinese white
Flowers of zinc
Oxozinc
Permanent white
Philosopher's wool
Zinc white
Properties
ZnO
Molar mass 81.38 g/mol
Appearance White solid
Odor Odorless
Density 5.606 g/cm3
Melting point 1,975 °C (3,587 °F; 2,248 K) (decomposes)
Boiling point Decomposes
0.00042 g/100 ml (18 °C) (slowly hydrolyzes)
Solubility Reacts with acids and alkalis
Insoluble in alcohols, esters, ethers, halocarbons
Vapor pressure ~0 mmHg
Thermochemistry
43.9 J·K−1·mol−1
-348.0 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
240 mg/kg (rat, intraperitoneal)
7,950 mg/kg (rat, oral)
2,500 mg/kg (mouse)
Related compounds
Related compounds
Cadmium oxide
Mercury(II) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Zinc oxide is a white oxide of zinc used an additive in many products. It has the formula ZnO.

Properties

Physical

Zinc oxide is white, powdery substance. It is insoluble in water. It will decompose before melting when heated to 1975°C, or to 950°C with carbon.

Chemical

Zinc oxide is amphoteric. It reacts with acids to form salts of zinc, and with bases to form zincates. It is used industrially to make zinc sulfide through reaction with hydrogen sulfide.[1]

Crystalline zinc oxide is thermochromic, changing from white to yellow when heated and in air 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.

Availability

Like most chemicals, zinc oxide can be purchased from scientific suppliers like Elemental Scientific in pure form.[2] It can also be purchased from art and ceramic suppliers, since it is used as a pigment and in glazes. However, some ZnO pigments are calcinated, which makes them inert to most reagents.

Preparation

Zinc oxide can be made in the lab by heating zinc carbonate or zinc hydroxide at high temperatures.

A more clean method involves electrolyzing a solution of sodium bicarbonate with a zinc anode. Zinc hydroxide and hydrogen gas are produced. The zinc hydroxide is pyrolyzed to zinc oxide.

It is also a side product of zinc melting. If the floating slag becomes yellow at high temperatures, then it contains zinc oxide.

Projects

  • Thermochromism demonstration
  • Make zinc oxide eugenol
  • Make zinc metal
  • Grow large crystals via hydrothermal growth[3]
  • Ceramic materials

Handling

Safety

Zinc oxide is non-toxic, but it's generally best to avoid breathing it in as it could potentially irritate the airways. Impure zinc often contains cadmium, which is extremely toxic to oneself and the environment.

Storage

Zinc oxide does not require special storage, though it should be kept away from any acidic vapors.

Disposal

Zinc oxide poses little toxicity to the environment, though it may contain traces of cadmium.

References

  1. http://en.wikipedia.org/wiki/Zinc_oxide
  2. http://www.elementalscientific.net/store/scripts/prodView.asp?idproduct=2857
  3. http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1964.tb14632.x/abstract

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