Monomer for poly(chloroethene) is chloroethene

Steps:

• Poly(chloroethene) is a polymer with repeating -CH2-CHCl- units.
• The monomer must be an alkene that adds via polymerization to form this chain.
• Chloroethene (CH2=CHCl) has the double bond and chlorine substituent matching the polymer structure.
• Confirm by naming: poly(chloroethene) directly derives from chloroethene monomer.

Why C is correct:

• Option C is CH2=CHCl, the vinyl chloride structure that polymerizes to poly(chloroethene) by addition across the C=C bond.

Why the others are wrong:

• A is ethene (CH2=CH2), which forms polyethylene without chlorine.
• B is chloroethane (CH3CH2Cl), a saturated compound unable to polymerize via addition.
• D is 1,1-dichloroethene (CH2=CCl2), which forms a different polymer with two chlorines per unit.

Final answer: C