Term: Carbon dioxide

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**Chemical and Physical Properties of Carbon Dioxide:**
– Chemical compound formula CO2, linear molecule with one carbon atom double bonded to two oxygen atoms.
– Exists as a gas at room temperature, acts as a greenhouse gas absorbing infrared radiation.
– Soluble in water forming carbonate and bicarbonate, leading to ocean acidification.

**Sources, Impact on Climate Change, and Environmental Effects:**
– Trace gas in Earth’s atmosphere at 421 ppm, primarily from burning fossil fuels.
– Plants use CO2 for photosynthesis, releasing oxygen, while excess CO2 is absorbed by land and ocean carbon sinks.
– Elevated CO2 levels lead to ocean acidification, impacting marine ecosystems and biodiversity.

**Industrial and Everyday Uses of Carbon Dioxide:**
– Inert gas in welding and fire extinguishers, pressurizing gas in air guns and oil recovery.
– Supercritical fluid solvent in decaffeination, byproduct of fermentation in food and beverage production.
– Added to carbonated beverages for effervescence.

**Biological Role, Photosynthesis, and Carbon Fixation:**
– End product of cellular respiration, transported in blood, and exhaled.
– Carbon fixation incorporates CO2 into organic molecules through photosynthesis.
– Plants, algae, and cyanobacteria use CO2 for food production, enhancing growth and yield of crops.

**Health Effects, Toxicity, and Monitoring of Carbon Dioxide:**
– CO2 not toxic but can cause drowsiness, suffocation, and asphyxiation at higher concentrations.
– Long-term exposure affects cognition and physical performance, with occupational exposure limits set.
– Proper ventilation crucial for maintaining safe indoor CO2 levels, with monitoring needed for occupant safety.

Carbon dioxide (Wikipedia)

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 (HCO3), which causes ocean acidification as atmospheric CO2 levels increase.

Carbon dioxide
Structural formula of carbon dioxide with bond length
Ball-and-stick model of carbon dioxide
Ball-and-stick model of carbon dioxide
Space-filling model of carbon dioxide
Space-filling model of carbon dioxide
IUPAC name
Carbon dioxide
Other names
  • Carbonic acid gas
  • Carbonic anhydride
  • Carbonic dioxide
  • Carbonic oxide
  • Carbon(IV) oxide
  • Methanedione
  • R-744 (refrigerant)
  • R744 (refrigerant alternative spelling)
  • Dry ice (solid phase)
3D model (JSmol)
ECHA InfoCard 100.004.271 Edit this at Wikidata
EC Number
  • 204-696-9
E number E290 (preservatives)
MeSH Carbon+dioxide
RTECS number
  • FF6400000
UN number 1013 (gas), 1845 (solid)
  • InChI=1S/CO2/c2-1-3 checkY
  • InChI=1/CO2/c2-1-3
  • O=C=O
  • C(=O)=O
Molar mass 44.009 g·mol−1
Appearance Colorless gas
  • Low concentrations: none
  • High concentrations: sharp; acidic
  • 1562 kg/m3 (solid at 1 atm (100 kPa) and −78.5 °C (−109.3 °F))
  • 1101 kg/m3 (liquid at saturation −37 °C (−35 °F))
  • 1.977 kg/m3 (gas at 1 atm (100 kPa) and 0 °C (32 °F))
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) Carbonic acid:
pKa1 = 3.6
pKa1(apparent) = 6.35
pKa2 = 10.33
−20.5·10−6 cm3/mol
Thermal conductivity 0.01662 W·m−1·K−1 (300 K (27 °C; 80 °F))
  • 14.90 μPa·s at 25 °C (298 K)
  • 70 μPa·s at −78.5 °C (194.7 K)
0 D
37.135 J/(K·mol)
214 J·mol−1·K−1
−393.5 kJ·mol−1
V03AN02 (WHO)
NFPA 704 (fire diamond)
Lethal dose or concentration (LD, LC):
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
Related carbon oxides
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).
☒N verify (what is checkY☒N ?)

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 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.

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