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Carbon dioxide


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Carbon dioxide gas is formed from the combination of two elements: carbon and oxygen. It is produced from the combustion of coal or hydrocarbons, the fermentation of liquids and the breathing of humans and animals.
It is found in small proportions in the atmosphere and is assimilated by plants which in turn produce oxygen. Carbon dioxide is a small but important constituent of air. Its typical co
ncentration is about 0.036% or 360 ppm. Exhaled air contains as much as 4% carbon dioxide.

Physical Properties of CO2

CO2 gas has a slightly irritating odor, is colorless and heavier than air.
It cannot sustain life.
It freezes at -78.5 °C to form carbon dioxide snow.
Liquid density : 1032 kg/m3 • Liquid/gas equivalent: 845 vol/vol
Depending on temperature and pressure, CO2 is a gas that exists in a gaseous, liquid or solid state.
Colorless
Inert, non flammable
Odorless
Taste is neutral.
Non toxic
Bacteriostatic

Chemical Properties of CO2

In an aqueous solution it forms carbonic acid, which is too unstable to be easily isolated.
Latent heat of vaporization : 571.08 kJ/kg
Vapor pressure : 58.5 bar
It will not burn or support combustion.

CARBON DIOXIDE

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CARBON DIOXIDE WAS discovered over 250 years ago by the 24-year old Englishman Joseph Black. He prepared and characterized samples of CO2(g)which he called fixed air. He found that the gas could be produced by heating chalk which lost mass during the heating process. We now know this reaction is:
CaCO3(s) CaO(s) + CO2(g)
Carbon dioxide is a colorless gas present in our atmosphere at very low levels. The level of CO2 have been rising throughout the 20th century which is believed to cause the greenhouse effect by which the earth's atmosphere is slowly warming up. Carbon dioxide is essentially odorless, however it causes a sharp sensation in one's nose when inhaled — such as from the bubbles of a carbonated beverage.
Carbon dioxide has many important uses. It is used in fire extinguishers, the soft drink industry, and as a chemical reagent to make other compounds. The major use of carbon dioxide is as a refrigerant (accounting for over 50%). Dry ice, CO2(s) was first commercially introduced as a refrigerant in 1924. Dry ice sublimes to a gas at -78.5 ºC at standard pressure. By the 1960s dry ice was replaced by liquid CO2 (commonly called liquid carbonic) as the most common CO2-refrigerant. Carbon dioxide has a melting point of -56.6 ºC at 5.2 atmospheres. Liquid CO2 is used to freeze materials such hamburger meat and metals and this improves the grindability of the material. It is also used to rapidly cool loaded trucks and rail cars. Another 25% of all CO2 produced is used in the soft drink industry. Carbon dioxide is now widely used as the propellant i
aerosol cans.
Carbon dioxide is manufactured by the combustion of hydrocarbons such as natural gas:
CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) ΔHºrxn = -803 kJ
The solubility of CO2(g) in water is 3.48 g per L at 0 ºC and 1.45 g/L at 25 ºC. This is equivalent to 1.77 mL CO2 per 1 mL water at 0 ºC and 0.74 mL CO2 per 1 mL water at 25 ºC. When CO2(g) dissolves in water it produces CO2(aq) for the most part. Solutions of CO2(aq) last longer if they are kept cool. As the solution of CO2(aq) is warmed, CO2(g) is released as bubbles.
CO2(aq) CO2(g)
The density of CO2(g) is over 50% greater than that of air. At 25 ºC and standard pressure, the density of carbon dioxide is 1.799 g/L, compared with 1.18 g/L for air.