Question 1: Define addition polymerisation in your own words.

Answer: Addition polymerisation is a chemical process where unsaturated monomers, such as alkenes, link together through the opening of double bonds to form long-chain polymers without producing any by-products.

Question 2: Describe the role of a catalyst in addition polymerisation.

Answer: A catalyst, such as a Ziegler-Natta catalyst or heat and pressure, helps speed up the polymerisation process by lowering the activation energy required for the double bonds to open and link together.

Question 3: Explain why addition polymers are considered to be unreactive under normal conditions.

Answer: Addition polymers are unreactive because their double bonds are already used up during polymerisation, and their long chains are stable under normal conditions.

Question 1: Calculate the molecular formula of the monomer ethene (C₂H₄) and the repeat unit of its polymer, polyethene.

Answer: Monomer: C2H4; Repeat unit: (C2H4)n

Question 2: If 5 grams of ethene are polymerized, how many moles of ethene are used? (Atomic weights: C=12 g/mol, H=1 g/mol)

Answer: Molecular weight of ethene = (2×12) + (4×1) = 24 + 4 = 28 g/mol. Moles = 5 g / 28 g/mol ≈ 0.179 moles.

Question 1: Describe a simple experimental setup to initiate addition polymerisation of ethene.

Answer: A typical setup includes a pressure vessel containing ethene gas, a catalyst such as a trace of oxygen or a metal catalyst, and conditions of elevated temperature and pressure to facilitate polymerisation.

Question 2: Identify two variables that can affect the rate of addition polymerisation.

Answer: Temperature and concentration of the monomer are two variables that affect the rate of polymerisation.

Question 3: List two safety precautions that should be taken during the polymerisation process.

Answer: Ensure proper ventilation to avoid accumulation of flammable gases and wear protective gloves and goggles to prevent contact with chemicals.

Question 1: A sample of polyvinyl chloride (PVC) is subjected to heating. The temperature is increased gradually, and the polymer's stability is observed. Explain what typically happens to PVC at high temperatures and why.

Answer: PVC tends to decompose at high temperatures, releasing hydrogen chloride gas due to the breakdown of its polymer chains. This occurs because the heat provides enough energy to break the bonds within the polymer, leading to thermal degradation.

Question 1: Explain how addition polymerisation is used in the manufacturing of polyethylene plastic bags.

Answer: Polyethylene is produced by the addition polymerisation of ethene monomers. Under suitable conditions, ethene molecules open their double bonds and link together to form long chains, which are then cooled and processed into plastic bags. This process is efficient, produces durable materials, and allows for large-scale manufacturing.

Question 2: Multiple Choice: Which of the following is a characteristic of addition polymers?

Answer: They are formed by the addition of monomers with double bonds.

Question 3: Fill in the blank: The repeat unit of polypropene (polypropylene) is __________.

Answer: (C3H6)n