Question

Polymerization of ethylene gives ________.
A) Propylene
B) Acetylene
C) Polyethylene
D) Polyacetylene

Answer 1

Hint: The process by which a large number of monomers combine together to form a polymer is called polymerization. In the polymerization of ethylene, ethylene, having chemical formula $C{H_2} = C{H_2}$ is a monomer.

Complete Solution :
- A polymer is defined as a large molecule of high molecular weight formed by the combination of a number of one or two types of molecules of low molecular weight. The smaller molecules which occur as repeating units to make up a polymer are known as monomers. The process by which monomers combine together to form a polymer is called polymerization.
- Chemical formula of ethylene is $C{H_2} = C{H_2}$. During polymerization of ethylene, thousands of ethylene molecules will join together to form the polymer called polyethylene. It is an addition polymerization. Addition polymerization occurs in monomer units having double bonds or triple bonds. It includes the combination of a large number of monomer units by the addition reaction. Thus, the polymerization reaction of ethylene to give polyethylene by addition reaction is as shown below:
 

When ethylene monomers polymerize to give the polymer, the pi-bonds are broken and a long chain of $ - C{H_2} - C{H_2} - $ units is produced. In the resulting polymer i.e. polyethylene, all the carbon-carbon bonds are single bonds.
So, the correct answer is “Option C”.

Note: In the formation of addition polymers, like polyethylene, the reaction is initiated by a catalyst, which results in the formation of a reactive intermediate. This intermediate then adds on to the monomer unit like ethylene to generate a new intermediate, which adds on to another monomer unit and the process goes on. Thus it is also known as chain growth polymerization.