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In elemental state, oxygen is a gas in the atmosphere and is dissolved in water. The amount of relatively reactive oxygen elemental remains constant only in long run, because O2 producing plants replace much as of aerobic breathing creatures as well as other combustion processes is used again (oxygen for energy). Without this biological cycle O2 would only occur in compounds, ie elemental O2 exists in a dynamic equilibrium.
The development of O2 concentration in atmosphere is described in article Development of earth's atmosphere. The O2 allotrope O3 Ozone is present in atmosphere at low concentrations. In space, O2 is the third most abundant element after hydrogen and helium. The mass fraction of O2 is in solar system about 0.8% (this corresponds to an (atomic) number fraction of about 500 ppm).
Some oxygen-rich inorganic compounds such as potassium permanganate, potassium nitrate (saltpeter), potassium chlorate and potassium chromate enter upon heating or reaction with reducing agents from oxygen. A further possibility of producing O2 in laboratory, is the decomposition of hydrogen peroxide on platinum-plated nickel foil. Pure O2 can be obtained by electrolysis of 30% potassium hydroxide solution of nickel electrodes. It Hydrogen and O2 are separated.
O2 is slightly soluble in water. The solubility depends on the pressure and the temperature. It increases with decreasing temperature and increasing pressure. At 0 degrees C and an O2 partial pressure of air of 212 hPa dissolve in pure water 14.16 mg / l oxygen. In oxygen-gas discharge Spectrum, the molecular orbitals of O2 are stimulated to emit light. The operating conditions are a pressure of 5-10 mbar, a high voltage of 1.8 kV, a current of 18 mA and a frequency of 35 kHz. During the recombination of ionized gas molecules, the characteristic color spectrum is emitted. In this case, a small part, caused reversibly formed by the supply of energy ozone.
The binding and the properties of O2 molecule can be well explained by the molecular orbital model. The s and p atomic orbitals of individual atoms are assembled to form bonding and antibonding molecular orbitals. The 1s and 2s orbitals of O2 atoms are each to . Sigma.. Sub. S and . Sigma.. Sub. S - bonding and antibonding molecular orbitals.
Since these orbitals are completely filled with electrons, they do not contribute to binding. From the 2p orbitals are a total of six molecular orbitals with different energy level. The orbitals have this same energy. Electrons are distributed in molecular orbitals, it comes to following breakdown of eight p-electrons. These two valence electrons determine the properties of O2 molecule. O2 has allowed a total of three and energetically accessible quantum states for the distribution of these electrons.
The actual separation of nitrogen and O2 by distillation in two distillation columns with different pressures. The distillation is carried out in counter-current principle, that is by the condensation heat of evaporated gas flows upward, condensed liquid drips down. Since O2 has a higher boiling point than nitrogen, it condenses readily and collects at the bottom so, nitrogen at the top of column.
The separation takes place initially at 5-6 bar in so-called medium pressure column. The resulting oxygen-enriched liquid is then (pressure about 0.5 bar) further separated in low pressure column. Through the liquid O2 of low pressure column, gaseous nitrogen of high pressure column is passed. It liquefies this and heated with the votes condensation heat the liquid. The more volatile nitrogen is discharged and preferably remains purified liquid oxygen. This still contains the noble gases krypton and xenon, which are separated in a separate column.
The development of O2 concentration in atmosphere is described in article Development of earth's atmosphere. The O2 allotrope O3 Ozone is present in atmosphere at low concentrations. In space, O2 is the third most abundant element after hydrogen and helium. The mass fraction of O2 is in solar system about 0.8% (this corresponds to an (atomic) number fraction of about 500 ppm).
Some oxygen-rich inorganic compounds such as potassium permanganate, potassium nitrate (saltpeter), potassium chlorate and potassium chromate enter upon heating or reaction with reducing agents from oxygen. A further possibility of producing O2 in laboratory, is the decomposition of hydrogen peroxide on platinum-plated nickel foil. Pure O2 can be obtained by electrolysis of 30% potassium hydroxide solution of nickel electrodes. It Hydrogen and O2 are separated.
O2 is slightly soluble in water. The solubility depends on the pressure and the temperature. It increases with decreasing temperature and increasing pressure. At 0 degrees C and an O2 partial pressure of air of 212 hPa dissolve in pure water 14.16 mg / l oxygen. In oxygen-gas discharge Spectrum, the molecular orbitals of O2 are stimulated to emit light. The operating conditions are a pressure of 5-10 mbar, a high voltage of 1.8 kV, a current of 18 mA and a frequency of 35 kHz. During the recombination of ionized gas molecules, the characteristic color spectrum is emitted. In this case, a small part, caused reversibly formed by the supply of energy ozone.
The binding and the properties of O2 molecule can be well explained by the molecular orbital model. The s and p atomic orbitals of individual atoms are assembled to form bonding and antibonding molecular orbitals. The 1s and 2s orbitals of O2 atoms are each to . Sigma.. Sub. S and . Sigma.. Sub. S - bonding and antibonding molecular orbitals.
Since these orbitals are completely filled with electrons, they do not contribute to binding. From the 2p orbitals are a total of six molecular orbitals with different energy level. The orbitals have this same energy. Electrons are distributed in molecular orbitals, it comes to following breakdown of eight p-electrons. These two valence electrons determine the properties of O2 molecule. O2 has allowed a total of three and energetically accessible quantum states for the distribution of these electrons.
The actual separation of nitrogen and O2 by distillation in two distillation columns with different pressures. The distillation is carried out in counter-current principle, that is by the condensation heat of evaporated gas flows upward, condensed liquid drips down. Since O2 has a higher boiling point than nitrogen, it condenses readily and collects at the bottom so, nitrogen at the top of column.
The separation takes place initially at 5-6 bar in so-called medium pressure column. The resulting oxygen-enriched liquid is then (pressure about 0.5 bar) further separated in low pressure column. Through the liquid O2 of low pressure column, gaseous nitrogen of high pressure column is passed. It liquefies this and heated with the votes condensation heat the liquid. The more volatile nitrogen is discharged and preferably remains purified liquid oxygen. This still contains the noble gases krypton and xenon, which are separated in a separate column.
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