Polystyrene is used to make Styrofoam cups. Which functional group is present in the repeating unit of polystyrene?

• A. Aromatic ring (benzene)
• B. Amine
• C. Carboxylic acid
• D. Alcohol

Answer: (A)

Verified step by step guidance

1. Identify the structure of the repeating unit of polystyrene. Polystyrene is a polymer made from the monomer styrene, which contains a benzene ring attached to an ethylene group.
2. Recall that a functional group is a specific group of atoms within a molecule that is responsible for characteristic chemical reactions of that molecule.
3. Examine the repeating unit of polystyrene and note the presence of a six-carbon ring with alternating double bonds, which is characteristic of an aromatic ring (benzene).
4. Compare the options given: amine (contains -NH2), carboxylic acid (contains -COOH), alcohol (contains -OH), and aromatic ring (benzene). Only the aromatic ring matches the structure in polystyrene.
5. Conclude that the functional group present in the repeating unit of polystyrene is the aromatic ring (benzene), which is responsible for many of its chemical properties.