Ozone by mozy 2000

Ozone

History

Ozone, the first allotrope of a chemical element to be recognized, was proposed as a distinct chemical substance by Christian Friedrich Schönbein in 1840, who named it after the Greek verb ozein (ὄζειν, "to smell"), from the peculiar odor in lightning storms.^[3][4] The formula for ozone, O₃, was not determined until 1865 byJacques-Louis Soret^[5] and confirmed by Schönbein in 1867.^[3][6]

Physical properties

Ozone is a pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such ascarbon tetrachloride or fluorocarbons, where it forms a blue solution. At 161 K (–112 °C), it condenses to form a dark blue liquid. It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below 80 K (–193 °C), it forms a violet-black solid.^[7]

Most people can detect about 0.01 μmol/mol of ozone in air where it has a very specific sharp odor somewhat resembling chlorine bleach. Exposure of 0.1 to 1 μmol/mol produces headaches, burning eyes, and irritation to the respiratory passages.^[8] Even low concentrations of ozone in air are very destructive to organic materials such as latex, plastics, and animal lung tissue.

Ozone is diamagnetic, which means that its electrons are all paired. In contrast, O₂ is paramagnetic, containing two unpaired electrons.

Structure

According to experimental evidence from microwave spectroscopy, ozone is a bent molecule, with C_2vsymmetry (similar to the water molecule). The O – O distances are 127.2 pm. The O – O – O angle is 116.78°.^[9] The central atom is sp² hybridized with one lone pair. Ozone is a polar molecule with adipole moment of 0.53 D.^[10] The bonding can be expressed as a resonance hybrid with a single bondon one side and double bond on the other producing an overall bond order of 1.5 for each side.

Reactions

Ozone is a powerful oxidizing agent, far stronger than O₂. It is also unstable at high concentrations, decaying to ordinary diatomic oxygen (with a half-life of about half an hour in atmospheric conditions):^[11]

2 O₃ → 3 O₂

This reaction proceeds more rapidly with increasing temperature and increased pressure. Deflagrationof ozone can be triggered by a spark, and can occur in ozone concentrations of 10 wt% or higher.^[12]

Ozone will oxidize most metals (except gold, platinum, and iridium) to oxides of the metals in their highest oxidation state. For example: