74 (iii) Write the name and formula of monomer of polyethylene.

Part I - Name of monomer

Polyethene is a polymer made up of a chain of ethylene as its monomer units which are joined together to form long polymeric chains.

• If polyethylene is made of a linear chain of its monomer (ethylene) units then it leads to the formation of High-density polyethylene
• If the polyethylene is the main linear chain that also has side branches, then it leads to the formation of Low-density polyethylene.

Part II - Formula and reaction of monomer

• The formula of ethylene molecule (monomer) is ${\mathrm{CH}}_2={\mathrm{CH}}_2$.
• The reaction of polymerization of polyethylene is shown below

$\underset{\mathrm{Ethylene}}{\mathrm{n}{\mathrm{CH}}_2={\mathrm{CH}}_2}\stackrel{\mathrm{Polymerise}}{\to }\underset{\mathrm{Polyethylene}}{{({\mathrm{CH}}_2={\mathrm{CH}}_2)}_{\mathrm{n}}}$