Calcium Carbide

Pure calcium carbide, CaC₂, is a colourless compound. It is a very important compound because it is used to produce ethyne (acetylene) which is itself an extremely important industrial compound. The combustion of ethyne (acetylene) in oxyacetylene welding and cutting produces a flame of over 3300^oC, making it the third hottest natural chemical flame, it and releases 11.8kJ/g of energy.

Calcium carbide is produced in an electric arc furnace in which a mixture of lime, CaO, and coke, C, is heated to about 2000^oC. The products of the reaction are calcium carbide and carbon monoxide gas. This reaction produces a calcium carbide yield of approximately 80%.

Calcium carbide reacts with water to produce ethyne (acetylene) and calcium hydroxide. The ethyne produced in this reaction can be used directly in combustion reactions such as in oxyacteylene welding and cutting, as well as in carbide lamps which are still in use in mines in some less wealthy countries.

Further Reading
http://www.ausetute.com.au/namsynes.html
http://www.ausetute.com.au/intrafor.html
http://www.ausetute.com.au/balcheme.html
http://www.ausetute.com.au/combusta.html
http://www.ausetute.com.au/tempconv.html
http://www.ausetute.com.au/enthchan.html
http://www.ausetute.com.au/manienth.html
http://www.ausetute.com.au/percentc.html
http://www.ausetute.com.au/yield.html

Study Questions

1. Write the molecular and structural formula for ethyne (acetylene).
2. What type of bonding is present in the calcium carbide compound? Explain your answer.
3. Write a balanced chemical equation for the reaction between lime and coke.
   
4. Write a balanced chemical equation for the production of ethyne (acetylene) from calcium carbide.
5. Convert these temperatures in ^oC to Kelvin:
   • 3300^oC
   • 2000^oC


6. Is the combustion of ethyne (acetylene) an endothermic or an exothermic reaction? Explain your answer.
7. Calculate the energy released during the combustion of :
   • 5kg of ethyne (acetylene)
   • 500g of ethyne (acetylene)
8. Calculate the energy released from the combustion of
   • 5 moles of ethyne (acetylene)
   • 0.1moles ethyne (acetylene)
9. Calculate the percentage composition of
   • calcium carbide
   • ethyne (acetylene)
10. Explain what is meant by the statement below:
    "This reaction produces a calcium carbide yield of approximately 80%".