Carbon Dioxide

Carbon dioxide, CO2, is one of two oxides of carbon, and it is the principal product oxide of carbon formed from the compustion of hydrocarbon fuels. Carbon dioxide is the focus of public concern in recent years due to the increasing concentration of this gas in the atmosphere as a result of the combustion of fossel fuels. The gas is implicated in the Greenhouse Effect.

The carbon dioxide which is present in the atmosphere is produced by respiration and by combustion. However, it has a short residence time in this phase as it is both consumed by plants during photosynthesis.

Physical Properties of Carbon Dioxide

Carbon dioxide is a colourless odourless gas, which is soluble in water, in ethanol and in acetone.

Melting Point : -55.6 degC
Boiling Point : -78.5 degC
Density : 1.977

Preparation of Carbon Dioxide

Carbon dioxide is prepared

by treating any metallic carbonate with dilute mineral acids, or
```
CaCO3   +   2 HCl   ==>   CaCl2   +   H2O   +   CO2     
```

by heating carbonates of metals other than alkali metals.

		Heat    
MgCO3           ==>   MgO   +   CO2

Properties of Carbon Dioxide

Carbon dioxide is a linear covalent molecule.
Carbon dioxide is an acidic oxide and reacts with water to give carbonic acid.
```
CO2   +   H2O   ==>   H2CO3     
```

Carbon dioxide reacts with alkalis to give carbonates and bicarbonates.


CO2   +   NaOH   ==>    NaHCO3  
			Sodium  
			BiCarbonate     

NaHCO3   +   NaOH   ==>         Na2CO3  +  H2O  
				Sodium  
				Carbonate

Uses of Carbon Dioxide

Large quantities of solid carbon dioxide (i.e. in the form of dry ice) are used in processes requiring large scale refrigeration.
Carbon dioxide is also used in fire extinguishers as a desirable alternative to water for most fires. It is a constituent of medical gases as it promotes exhalation. It is also used in carbonated drinks.

Chemical Properties of Carbon Dioxide

Carbon dioxide is a linear covalent molecule.
Carbon dioxide is an acidic oxide and reacts with water to give carbonic acid.
```
	CO2   +   H2O   ==>   H2CO3     
```

Carbon dioxide reacts with alkalis to give carbonates and bicarbonates.


	CO2   +   NaOH   	==>;    	NaHCO3  
				Sodium  
				BiCarbonate     

	NaHCO3   +   NaOH   ==>         Na2CO3  +  H2O  
				Sodium  
				Carbonate