6CO2

6CO2 is a chemical notation used to indicate six molecules of carbon dioxide, or six moles of CO2 in macroscopic measurements, depending on the context. Carbon dioxide is a linear triatomic molecule with the structure O=C=O and carbon in the +4 oxidation state. In chemical equations, a coefficient such as 6 multiplies the formula unit, signaling that six units of CO2 participate in or are produced by the reaction.

Carbon dioxide is a colorless, non-flammable gas at room temperature that dissolves in water to form carbonic acid. It occurs naturally in Earth's atmosphere as a trace gas and is released by respiration, decay, and combustion of carbon-based fuels. It is a key product in many biological and industrial processes. In photosynthesis, six CO2 molecules react with six water molecules to produce one molecule of glucose and six molecules of O2: 6 CO2 + 6 H2O -> C6H12O6 + 6 O2. In cellular respiration, the reverse occurs: C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy. In complete combustion of organic matter, CO2 is formed in proportion to the carbon content; the coefficient 6 CO2 would appear in a balanced equation as needed.

Mass considerations: one mole of CO2 has a mass of about 44.01 grams, so six moles have a mass of about 264.06 grams. The concept of 6CO2 is widely used in stoichiometry for converting between amounts of substance, mass, and volume in gas-phase reactions, and it plays a central role in accounting for carbon flux in biological and environmental contexts.