Carbon Dioxide Molecular Formula

Carbon dioxide normally occurs as a colorless gas. In solid form, it is called dry ice. The chemical or molecular formula for carbon dioxide is CO₂. The central carbon atom is joined to two oxygen atoms by covalent double bonds. The chemical structure is centrosymmetric and linear, so carbon dioxide has no electric dipole.

Other Names for Carbon Dioxide

While "carbon dioxide" is the usual name for CO₂, the chemical goes by other names as well. The solid is called dry ice. The gas is called carbonic acid gas. More general names for the molecule are carbonic anhydride, carbonic dioxide, and carbon(IV) oxide. As a refrigerant, carbon dioxide is named R-744 or R744.

Why Water Is Bent and Carbon Dioxide Is Linear

Both water (H₂O) and carbon dioxide (CO₂) consists of atoms connected by polar covalent bonds. Yet, water is a polar molecule while carbon dioxide is nonpolar. The polarity of the chemical bonds within a molecule is not sufficient to make the molecule polar. Each water molecule has a bent shape because of the lone electron pair on the oxygen atom. Each C=O bond in carbon dioxide is polar, with the oxygen atom pulling the electrons from carbon toward itself. The charges are equal in magnitude, yet opposite in direction, so the net effect is to produce a nonpolar molecule.

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Dissolving Carbon Dioxide in Water

Carbon dioxide is soluble in water, where it acts as a diprotic acid, first dissociating to form the bicarbonate ion and then carbonate. A common misconception is that all dissolved carbon dioxide forms carbonic acid. Most dissolved carbon dioxide remains in molecular form.

Physical Properties

At low concentration, as in air, carbon dioxide is odorless and colorless. At high concentrations, carbon dioxide has a definite acidic scent.

At ordinary pressure, carbon dioxide has no liquid state. The solid sublimes directly into the gas. The gas deposits directly as a solid. The liquid form only occurs at pressure above 0.517 MPa. While dry ice is the familiar form of solid carbon dioxide, it forms an amorphous glass-like solid (carbonia) at high pressure (40-48 GPa). Carbonia is highly similar to regular glass, which is amorphous silicon dioxide (SiO₂). Above its critical point, carbon dioxide forms a supercritical fluid.

Health Effects and Toxicity

The body naturally produces around 1 kilogram or 2.3 pounds of carbon dioxide every day. The gas regulates the body's blood supply and regulates respiration. Most of this carbon dioxide gets converted into bicarbonate ions. Smaller percentages are dissolved in plasma or bound to hemoglobin. Ultimately, carbon dioxide carried in the blood is breathed out through the lungs.

While not technically a toxin, carbon dioxide is an asphyxiant gas. Most people feel drowsy or like the air is stuffy as CO₂ concentration approaches 1% of air. Concentrations between 7% and 10% can lead to suffocation, even when sufficient oxygen is present. Symptoms include headache, dizziness, hearing and vision problems, and unconsciousness.

Carbon Dioxide in Air

Carbon dioxide is a trace gas in air. While the concentration varies geographically, it averages around 0.04% or 412 parts per million. CO₂ levels are on the rise. In pre-industrial times, the level of carbon dioxide in air was about 280 ppm. Much of the increase in carbon dioxide is attributed to deforestation and the burning of fossil fuels. Carbon dioxide is a greenhouse gas, so the increase in its concentration produces global warming and ocean acidification.

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