Carbon Dioxide - CO2
Carbon Dioxide - C02
Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. It is often referred to by its formula CO2. It is present in the Earth’s atmosphere at a low concentration of approximately 0.04% and is an important greenhouse gas. In its solid state, it is called dry ice. It is a major component of the carbon cycle.
Origins
Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, and the respiration processes of living aerobic organisms; man-made sources of carbon dioxide come mainly from the burning of fossil fuels for heating, power generation and transport. It is also produced by various microorganisms from fermentation and cellular respiration. Plants convert carbon dioxide to carbohydrates during a process called photosynthesis. They produce the energy needed for this reaction through the photolysis of water. The resulting gas, oxygen, is released into the atmosphere by plants, which is subsequently used for respiration by heterotrophic organisms, forming a cycle.
Chemical and physical properties
Carbon dioxide is a colorless gas which, when inhaled at high concentrations (a dangerous activity because of the associated asphyxiation risk), produces a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucous membranes and saliva, forming a weak solution of carbonic acid. One may notice this sensation if one attempts to stifle a burp after drinking a carbonated beverage.
Its density at standard temperature and pressure is around 1.98 kg/m3, about 1.53 times that of air. The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole. As it is fully oxidized, it is not very reactive and is non-flammable.
At temperatures below −78 °C, carbon dioxide changes directly from a gas to a white solid called dry ice through a process called deposition. Liquid carbon dioxide forms only at pressures above 5.1 atm; at atmospheric pressure, it passes directly between the solid phase and the gaseous phase in a process called sublimation.
Industrial production
Carbon dioxide is manufactured mainly from six processes:
- As a byproduct in ammonia and hydrogen plants, where methane is converted to CO2;
- From combustion of carbonaceous fuels;
- As a byproduct of fermentation;
- From thermal decomposition of CaCO3;
- As a byproduct of sodium phosphate manufacture;
- Directly from natural carbon dioxide gas wells.
Atmospheric concentration
As of January 2007, the earth’s atmospheric CO2 concentration is about 0.0383% by volume (383 ppmv) or 0.0582% by weight. This represents about 2.996×1012 tonnes, and is estimated to be 105 ppm (37.77%) above the pre-industrial average.
Because of the greater land area, and therefore greater plant life, in the northern hemisphere as compared with the southern hemisphere, there is an annual fluctuation of up to 6 ppmv (± 3 ppmv), peaking in May and reaching a minimum in October at the end of the northern hemisphere growing season, when the quantity of biomass on the planet is greatest.
Despite its small concentration, CO2 is a very important component of Earth’s atmosphere, because it absorbs infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode) and enhances the greenhouse effect.
Information Courtesy of Wikipedia
