carbon dioxide

Carbon Dioxide




Molecular formula: CO2
Molecular weight: 44     

Occurance

Carbon dioxide is present in air of which it forms 0.03% by volume and comes in there as a result of the burning of fuels, respiration and decay of animal and vegetable matter. It is found in deep wells, caves and mines since it is heavier than air.

Laboratory preparation of Carbon dioxide

Apparatus required
1. Woulfe’s bottle
2. Thistle funnel
3. Delivery tube
4. Gas jar

Chemical required:

1. (CaCO3)
2. Hydrochloric acid (HCl)         




Principle:

When calcium carbonate is treated with hydrochloric acid, evolution of carbon dioxide takes place. The gas may be collected by upward displacement of air since it is heavier than air.
               CaCO3 + 2HCl = CaCl2 + CO2 + H2O

Procedure:

 

Lab preparation of carbon dioxide

Lab preparation of carbon dioxide

Take small pieces of calcium carbonate and put in a Woulfe’s bottle. Connect a delivery tube and a thistle funnel as shown in figure. The delivery tube leads gas produced into the gas jar. Through the thistle funnel allow dilute hydrochloric acid to pass in the bottle. The bubble of gas passes through the delivery tube.
 
Test the jar whether it is filled with the help of a burning match stick. It extinguishes when brought near its mouth.The principle of preparation of carbon dioxide gas is used to identify whether a stone is calcium carbonate.

Manufacture of Carbon dioxide

 

Manufacture of carbon-dioxide for industrial scale

     Manufacture of carbon-dioxide for industrial scale

In industrial scale carbon dioxide is prepared from calcium carbonate, in the presence of coal it is burnt as a result calcium oxide (Lime or quick lime) and carbon dioxide is produced.
               Calcium carbonate  = heat calcium oxide + carbon dioxide
                              CaCO3 = CaO + CO2
Carbon dioxide, thus, produced is collected and sent for use in the industries.
Calcium oxide is also called lime or quick lime. We use slaked lime or hydrated lime for white washing. When calcium oxide is treated with water hydrates lime (calcium hydroxide) is produced.
                              CaO + H2O = Ca (OH)2

Properties of Carbon dioxide

               Physical properties:

1. Carbon dioxide is colourless and odourless gas.
2. It is heavier than air (density 22). Because of this property it can be poured from one vessel into another vessel. In the caves, deep wells and mines carbon dioxide content is more due to its density.
3. It dissolves in water. When soda bottle opened the bobbles which comes is carbon dioxide.    

Chemical properties

1. Carbon dioxide is soluble in water which produces carbonic acid.     
   CO2 + H2O = H2CO3
  This acid turns blue litmus paper into red.
2. Carbon dioxide is non-combustible and non-supporter of combustion. But when burning piece of sodium magnesium or potassium introduced in a jar containing carbon dioxide we can see black spots and white powder which is carbon and oxide of metal respectively.     
          2Mg + CO2 =   2MgO + C
          4Na + 3CO2 = 2Na2CO3 + C
3. Lime water (clear solution) is turned milky when carbon dioxide is passed into it. This is due to the formation of insoluble calcium carbonate.
              Ca (OH)2 + CO2 = CaCO3 + H2O    
This property is used for test of a gas whether it is carbon dioxide.
If more carbon dioxide is passed in milky solution it turns into clear solution due to the formation of insoluble calcium bicarbonate.
                              CaCO3 + H2O + CO2 = Ca (HCO3)2

Use of Carbon dioxide

 

Fire extinguisher

           Fire extinguisher

1. In the preparation of aerated drinks such as soda water, carbon dioxide is used.
2. When carbon dioxide is cooled at about -78 C, it turns into ice (Dry ice). Dry ice is used as refrigeration and preservation of food stuffs.
3. Carbon dioxide is used by plants in photosynthesis which is the only process of trapping solar energy in natural form. Photosynthesis has made life possible since animals depend on plants.
4. Carbon dioxide is used in fire extinguishers. There are two chemicals in extinguishers which in contact produce carbon dioxide. This is heavier than air and make easier to extinguish fire.




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