Chemical and Physical Properties
– Carbon dioxide (CO2) is a chemical compound with the formula CO2.
– It consists of molecules with one carbon atom double bonded to two oxygen atoms.
– Carbon dioxide is a gas at room temperature and is transparent to visible light but absorbs infrared radiation.
– It is soluble in water and can be found in groundwater, lakes, ice caps, and seawater.
– Increasing levels of atmospheric CO2 cause ocean acidification.
– The carbon dioxide molecule has a linear and centrosymmetric structure.
– The carbon-oxygen bond length in CO2 is shorter than a typical single C-O bond.
– CO2 has four vibrational modes, including symmetric and antisymmetric stretching and degenerate bending modes.
– Some vibrational modes are observed in the infrared (IR) spectrum, while others are detected in Raman spectroscopy.
– In a Coulomb explosion imaging experiment, it was found that no gas-phase CO2 molecules are exactly linear.
– Carbon dioxide is soluble in water and can form carbonic acid (H2CO3) in a reversible reaction.
– The majority of CO2 in water remains as CO2 molecules and does not affect the pH.
– The relative concentrations of CO2, bicarbonate (HCO3-), and carbonate (CO3^2-) depend on the pH.
– In neutral or slightly alkaline water, the bicarbonate form predominates, while in very alkaline water, the carbonate form is predominant.
– The oceans contain about 120mg of bicarbonate per liter.
– Carbon dioxide is a trace gas in Earth’s atmosphere, currently at a concentration of 421 parts per million (ppm).
– The pre-industrial concentration of CO2 was around 280 ppm.
– Burning fossil fuels is the primary cause of increased CO2 concentrations and climate change.
– Plants, algae, and cyanobacteria use CO2 for photosynthesis, producing oxygen as a byproduct.
– CO2 is released into the atmosphere through decay, combustion, and volcanic activity.
Industrial and Everyday Uses
– Carbon dioxide is used as an inert gas in welding, fire extinguishers, and pressurizing gas in air guns and oil recovery.
– It is a supercritical fluid solvent in decaffeination processes and supercritical drying.
– CO2 is a byproduct of fermentation in bread, beer, and wine making, and is added to carbonated beverages for effervescence.
– It has an odorless characteristic at normal concentrations but can generate the taste of soda water.
– Carbon dioxide can be sequestered in rocks, coal, petroleum, and natural gas and released through burning fossil fuels or natural processes.
Chemical Reactions of CO2
– CO2 can react with amines to form carbamates, which is used in CO2 scrubbers and carbon capture and storage.
– Strong nucleophiles like Grignard reagents and organolithium compounds can react with CO2 to produce carboxylates.
– CO2 can serve as a ligand in metal carbon dioxide complexes, facilitating the conversion of CO2 to other chemicals.
– The reduction of CO2 to CO is a difficult and slow reaction.
– Photoautotrophs use CO2, sunlight, and water to produce simple sugars through photosynthesis.
Biological Role
– Carbon dioxide is produced as an end product of cellular respiration in organisms that obtain energy from breaking down sugars, fats, and amino acids.
– It is transported in the blood and exhaled by vertebrates or dissolved in water through the skin or gills of amphibians and fish.
– Plants, algae, aerobic fungi, and bacteria can absorb more CO2 during photosynthesis than they release in respiration.
– CO2 is an essential component for photosynthesis, where it is incorporated into energy-rich organic molecules.
– Ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) is the enzyme involved in the first step of carbon fixation during photosynthesis.
– Photosynthesis is the process by which plants convert carbon dioxide and water into oxygen and organic compounds.
– It is the primary source of oxygen in the atmosphere.
– Phototrophs, such as plants and algae, use photosynthesis to produce food for themselves and other organisms.
– Coccolithophores, a type of phototroph, synthesize hard calcium carbonate scales that can remain fixed for geological timescales.
– Photosynthesis by phytoplankton in the ocean promotes the absorption of carbon dioxide from the atmosphere.
Effects and Health Implications
– Plants can grow up to 50% faster in concentrations of 1,000ppm CO2 compared to ambient conditions.
– Elevated CO2 levels increase the harvestable yield of crops, such as wheat, rice, and soybean.
– Increased CO2 concentrations result in reduced water usage and increased water-use efficiency in plants.
– CO2 enrichment can lead to decreased concentrations of micronutrients in crop plants.
– High concentrations of CO2 can alter the concentration of secondary metabolites in plants.
– Carbon dioxide is not classified as toxic or harmful according to international standards.
– Concentrations up to 1% (10,000ppm) can make some people feel drowsy and give the lungs a stuffy feeling.
– Concentrations of 7% to 10% (70,000 to 100,000ppm) may cause suffocation and various physiological effects.
– In high concentrations, carbon dioxide can collect in sheltered/pocketed locations and suffocate animals.
– Long-term continuous exposure to CO2 levels below 1% has few studies on its health effects.
– Occupational CO2 exposure limits have been set at 0.5% (5000ppm) for an eight-hour period.
– At this concentration, International Space Station crew experienced various symptoms.
– Animal studies at 0.5% CO2 demonstrated kidney calcification and bone loss.
– Cognitive abilities can be negatively affected at concentrations as low as 0.1% (1000ppm) CO Source: https://en.wikipedia.org/wiki/Carbon_dioxide
Carbon dioxide is a chemical compound with the chemical formula CO2. It is made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature, and as the source of available carbon in the carbon cycle, atmospheric CO2 is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO−3), which causes ocean acidification as atmospheric CO2 levels increase.
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| Names | |||
|---|---|---|---|
| IUPAC name Carbon dioxide | |||
Other names
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| Identifiers | |||
3D model (JSmol) | |||
| 3DMet | |||
| 1900390 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.004.271 | ||
| EC Number |
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| E number | E290 (preservatives) | ||
| 989 | |||
| KEGG | |||
| MeSH | Carbon+dioxide | ||
PubChem CID | |||
| RTECS number |
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| UNII | |||
| UN number | 1013 (gas), 1845 (solid) | ||
CompTox Dashboard (EPA) | |||
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| Properties | |||
| CO2 | |||
| Molar mass | 44.009 g·mol−1 | ||
| Appearance | Colorless gas | ||
| Odor |
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| Density |
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| Critical point (T, P) | 304.128(15) K (30.978(15) °C), 7.3773(30) MPa (72.808(30) atm) | ||
| 194.6855(30) K (−78.4645(30) °C) at 1 atm (0.101325 MPa) | |||
| 1.45 g/L at 25 °C (77 °F), 100 kPa (0.99 atm) | |||
| Vapor pressure | 5.7292(30) MPa, 56.54(30) atm (20 °C (293.15 K)) | ||
| Acidity (pKa) | 6.35, 10.33 | ||
| −20.5·10−6 cm3/mol | |||
| Thermal conductivity | 0.01662 W·m−1·K−1 (300 K (27 °C; 80 °F)) | ||
Refractive index (nD) | 1.00045 | ||
| Viscosity |
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| 0 D | |||
| Structure | |||
| Trigonal | |||
| Linear | |||
| Thermochemistry | |||
Heat capacity (C) | 37.135 J/(K·mol) | ||
Std molar entropy (S⦵298) | 214 J·mol−1·K−1 | ||
Std enthalpy of formation (ΔfH⦵298) | −393.5 kJ·mol−1 | ||
| Pharmacology | |||
| V03AN02 (WHO) | |||
| Hazards | |||
| NFPA 704 (fire diamond) | |||
| Lethal dose or concentration (LD, LC): | |||
LCLo (lowest published) | 90,000 ppm (162,000 mg/m3)(human, 5 min) | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 5000 ppm (9000 mg/m3) | ||
REL (Recommended) | TWA 5000 ppm (9000 mg/m3), ST 30,000 ppm (54,000 mg/m3) | ||
IDLH (Immediate danger) | 40,000 ppm (72,000 mg/m3) | ||
| Safety data sheet (SDS) | Sigma-Aldrich | ||
| Related compounds | |||
Other anions | |||
Other cations | |||
| See Oxocarbon | |||
Related compounds | |||
| Supplementary data page | |||
| Carbon dioxide (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
It is a trace gas in Earth's atmosphere at 421 parts per million (ppm), or about 0.04% (as of May 2022) having risen from pre-industrial levels of 280 ppm or about 0.025%. Burning fossil fuels is the primary cause of these increased CO2 concentrations and also the primary cause of climate change.
Its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by organisms and geological phenomena. Plants, algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis, which produces oxygen as a waste product. In turn, oxygen is consumed and CO2 is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration. CO2 is released from organic materials when they decay or combust, such as in forest fires. Since plants require CO2 for photosynthesis, and humans and animals depend on plants for food, CO2 is necessary for the survival of life on earth.
Carbon dioxide is 53% more dense than dry air, but is long lived and thoroughly mixes in the atmosphere. About half of excess CO2 emissions to the atmosphere are absorbed by land and ocean carbon sinks. These sinks can become saturated and are volatile, as decay and wildfires result in the CO2 being released back into the atmosphere. CO2 is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas. Sequestered CO2 is released into the atmosphere through burning fossil fuels or naturally by volcanoes, hot springs, geysers, and when carbonate rocks dissolve in water or react with acids.
CO2 is a versatile industrial material, used, for example, as an inert gas in welding and fire extinguishers, as a pressurizing gas in air guns and oil recovery, and as a supercritical fluid solvent in decaffeination of coffee and supercritical drying. It is a byproduct of fermentation of sugars in bread, beer and wine making, and is added to carbonated beverages like seltzer and beer for effervescence. It has a sharp and acidic odor and generates the taste of soda water in the mouth, but at normally encountered concentrations it is odorless.
