Question 1: Define an addition reaction in the context of organic chemistry.

Answer: An addition reaction is a chemical process where atoms or groups are added to a molecule, typically across a double bond in alkenes, resulting in a single product.

Question 2: Describe the general mechanism of an addition reaction involving an alkene and hydrogen halides.

Answer: The alkene's double bond reacts with the hydrogen halide (HX), where the pi bond electrons attack the hydrogen atom, forming a carbocation intermediate, which then reacts with the halide ion (X-) to form a single product.

Question 3: What is the role of catalysts in addition reactions involving alkenes?

Answer: Catalysts, such as sulfuric acid, speed up addition reactions by providing an alternative pathway with lower activation energy, increasing the reaction rate.

Question 1: If 50 grams of ethene (C2H4) reacts completely with hydrogen bromide (HBr), how many moles of ethene are involved? (Atomic masses: C=12 g/mol, H=1 g/mol)

Answer: The molar mass of ethene (C2H4) = (2×12) + (4×1) = 24 + 4 = 28 g/mol. Moles = 50 g / 28 g/mol ≈ 1.79 mol.

Question 2: Calculate the volume of hydrogen gas (H2) at standard temperature and pressure (STP) needed to react completely with 2 moles of ethene in an addition reaction.

Answer: Reaction: C2H4 + H2 → C2H6. Moles of H2 needed = 2 mol. At STP, 1 mol of gas occupies 22.4 L. Volume = 2 mol × 22.4 L/mol = 44.8 L.

Question 1: Identify three variables that can affect the outcome of an addition reaction experiment involving alkenes.

Answer: Variables include temperature, concentration of reactants, and presence of a catalyst.

Question 2: List two safety precautions that must be observed when handling hydrogen halides in addition reactions.

Answer: Use in a well-ventilated area or fume hood, and wear protective gloves and goggles.

Question 3: Describe a typical setup for conducting an addition reaction involving an alkene and a halogen.

Answer: A typical setup includes a round-bottom flask connected to a condenser, with the alkene and halogen source added under controlled temperature. The reaction is carried out in a fume hood with appropriate protective gear, and safety measures include using gloves and eye protection.

Question 1: In an experiment, 10 grams of ethene reacted with excess bromine (Br2). The product was then purified and weighed as 16 grams of 1,2-dibromoethane. Explain what this data suggests about the reaction.

Answer: The increase in mass indicates the addition of bromine across the double bond of ethene, forming 1,2-dibromoethane. The data confirms a successful addition reaction, with the mass increase corresponding to the two bromine atoms added.

Question 1: Explain how addition reactions of alkenes are utilized in the manufacture of plastics or pharmaceuticals.

Answer: Addition reactions allow the transformation of simple alkenes into more complex compounds used in manufacturing plastics like polyethylene or pharmaceuticals. By adding functional groups or modifying molecular structures, these reactions help produce materials with desired properties, such as flexibility, durability, or biological activity.

Question 2: Which industry benefits most from the understanding of addition reactions involving alkenes, and why?

Answer: Petrochemical and plastics manufacturing