A polymer is a large molecule composed of many repeated units. What is a polyester composed of?

Options

A. Ether
B. Cellulose
C. Amino acids
D. Ester

Explanation

**Step-by-Step Solution:**

1. **Understanding Polymers:**
- A polymer is a large molecule made up of repeating structural units called monomers. These monomers are covalently bonded together to form long chains.

2. **Defining Polyester:**
- Polyester is a type of polymer that is formed through a specific type of reaction called condensation polymerization.

3. **Monomers of Polyester:**
- The primary monomers used to create polyesters are diols (which are alcohols with two hydroxyl groups) and dicarboxylic acids (which have two carboxylic acid groups).

4. **Common Examples:**
- A well-known example of polyester is polyethylene terephthalate (PET), which is made from the monomers ethylene glycol (a diol) and terephthalic acid (a dicarboxylic acid).

5. **Formation Process:**
- During the formation of polyester, the hydroxyl group from the diol reacts with the carboxylic acid group from the dicarboxylic acid, resulting in the release of water and the formation of an ester bond. This process repeats, leading to the growth of the polymer chain.

6. **Conclusion:**
- Therefore, polyester is composed of repeated units formed from the condensation of diols and dicarboxylic acids.

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