ozone

Examples of ozone in the following topics:

• Ozone Depletion

  • Free radicals in the upper stratosphere act as catalysts for ozone decomposition, thereby depleting the ozone layer.
  • Ozone depletion describes two distinct but related phenomena observed since the late 1970s: (1) a steady decline of about 4 percent per decade in the total volume of ozone in Earth's stratosphere (the ozone layer); and (2) a much larger springtime decrease in stratospheric ozone over Earth's polar regions.
  • The latter phenomenon is referred to as the ozone hole.
  • The largest ozone hole was observed in September, 2006.
  • The reaction of these free radicals with ozone disrupts the ozone-oxygen cycle, leading to the destruction of stratospheric ozone and the depletion of the ozone layer.

• Polar Ozone Holes

  • Chlorofluorocarbons have disrupted stratospheric ozone generation, resulting in a thinning of the ozone layer at the poles.
  • The chlorine radical can then react with ozone, as shown below:
  • The chlorine breaks an oxygen off from ozone, producing diatomic oxygen.
  • Having destroyed two ozone molecules, the chlorine radical is produced once more and can destroy more ozone molecules.
  • CFCs have caused a gradual decrease in ozone levels throughout the stratosphere.

• Air Pollution

  • Decreased stratospheric ozone: a depletion in ozone levels caused by the release of refrigerants, which produce free radicals that catalyze the decomposition of ozone.
  • Increased ozone concentrations at ground levels: an increase in surface ozone that contributes to smog.

• Ozone

  • In total, ozone makes up only 0.6 parts per million of the atmosphere.
  • This makes ozone a potent respiratory hazard and pollutant near ground level.
  • However, the so-called ozone layer (a portion of the stratosphere with a higher concentration of ozone, from two to eight ppm) is beneficial.
  • It is dangerous to allow this liquid to warm to its boiling point because both concentrated gaseous ozone and liquid ozone can detonate.
  • Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation.

• Earth's Atmosphere

  • While the three major components have remained relatively constant over time and space, the minor components, which also include methane, sulfur dioxide, ozone, and nitrogen oxides, have varied more widely.
  • The next layer, the stratosphere, contains an ozone layer that results from the reaction of ionizing solar radiation with oxygen gas; this ozone layer is responsible for the absorption of UV light.
  • In the recent past, we have damaged our ozone layer by putting chlorofluorocarbons (CFCs) into the atmosphere.
  • The CFCs have damaged ozone, resulting in a hole in the ozone layer.
  • In recent years, CFCs have been banned and the ozone layer hole is shrinking.

• Photochemical Smog

  • Ultraviolet light can split nitrogen dioxide into nitric oxide and monatomic oxygen; this monatomic oxygen can then react with oxygen gas to form ozone.
  • Products like ozone, aldehydes, and peroxyacetyl nitrates are called secondary pollutants.
  • These oxidizing compounds have been linked to a variety of negative health outcomes; ozone, for example, is known to irritate the lungs.

• The Rate Law

  • The reaction between nitric oxide and ozone, $NO(g) + O_3(g)\rightarrow NO_2(g) + O_2(g)$ , is first order in both nitric oxide and ozone.

• Ultraviolet Light

  • In addition to short wave UV blocked by oxygen, a great deal (>97%) of mid-range ultraviolet (almost all UV above 280 nm and most up to 315 nm) is blocked by the ozone layer, and like ionizing short wave UV, would cause much damage to living organisms if it penetrated the atmosphere.
  • Most UV-B and all UV-C is absorbed by ozone (O3) molecules in the upper atmosphere.
  • Most UV wavelengths are absorbed by oxygen and ozone in Earth's atmosphere.

• Elements of Life

  • The Oparin-Haldane hypothesis suggests that the atmosphere of the early Earth may have been chemically reducing in nature, composed primarily of: methane (CH4), ammonia (NH3), water (H2O), hydrogen sulfide (H2S), carbon dioxide (CO2) or carbon monoxide (CO), with phosphate (PO43-), molecular oxygen (O2) and ozone (O3) either rare or absent.

• Hydroboration Reactions and Oxidations

  • Reactions of alkynes with oxidizing agents such as potassium permanganate and ozone usually result in cleavage of the triple-bond to give carboxylic acid products.