Give a few uses of ethene.


  1. No. iv. Give a few uses of ethene.

Answer. Ethene is used:

  1. For artificial ripening of fruits
  2. As a general anaesthetic

iii. For manufacture of polythene. Polythene is a plastic material used in      packaging, toys, bags.

  1. As a starting material for the manufacture of a large number of compounds such as ethylene oxide, ethyl alcohol, ethylene glycol, diethyl ether, etc.; ethylene oxide is used as a fumigant, ethylene glycol is used as an anti freeze, and diethyl ether and ethyl alcohol are used as solvents
  2. For making poisonous mustard gas which is used in chemical warfare.
  1. No. v. Which gases are present in LPG?

Answer. Propane and butane gases are present in LPG

Test Yourself 12.4 (ALKYNES)

  1. No. i. Why the alkynes are called acetylenes?

Answer. Alkynes are also called acetylenes because of the name of the first member of the series is acetylene.

  1. No. ii. How is tetrabromoethane prepared from acetylene?

Answer. When bromine water is added to acetylene, red-brown colour of bromine water is discharged rapidly due to formation of colorless tetrabromoethane.

Br    Br

HC≡CH +   2Br2   →  H-C — C-H

Br    Br


  1. No.iii. How can you prepare acetylene from tetrachloroethane?

Answer. When tetrachloroethane is heated with Zinc dust, the elimination of halogen atoms takes place and acetylene is formed.

   Cl  Cl                      heat

 H-C―C-H   + 2Zn (dust)           HC≡CH + 2ZnCl2

   Cl  Cl

  1. No.iv. What is the difference between glycol and glyoxalin?

Answer. The formula of glycol is:



It is (1,2-ethandiol): It belongs to alcohol family.

The formula of glyoxal is:


║ ║



It does not belong to alcohol family.


  1. No. v. Write the formula of oxalic acid

Answer. The formula of oxalic acid is:


║ ║


oxalic acid

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