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

Answer: An addition reaction is a chemical process where two or more molecules combine to form a larger molecule, typically involving the addition of atoms or groups across a double bond in alkenes.

Question 2: Describe the general mechanism of an electrophilic addition reaction with alkenes.

Answer: In electrophilic addition, the electron-rich double bond in the alkene reacts with an electrophile, forming a carbocation intermediate, followed by nucleophilic attack to produce the addition product.

Question 3: Name two common reagents used in addition reactions with alkenes.

Answer: Hydrogen bromide (HBr) and bromine water (Br₂ in water).

Question 1: Calculate the number of moles of H₂ needed to fully hydrogenate 2 mol of ethene (C₂H₄). Assume complete reaction.

Answer: H₂ needed = 2 mol of H₂ (since 1 mol of H₂ reacts with 1 mol of C₂H₄).

Question 2: If 50 mL of bromine water reacts with 0.1 mol of an alkene, what is the concentration of bromine water in mol/L?

Answer: Concentration = 0.1 mol / 0.05 L = 2 mol/L.

Question 1: Design a simple experiment to test if an unknown alkene reacts via an addition reaction with bromine water.

Answer: Add a few drops of bromine water to the unknown alkene in a test tube. Observe if the bromine water decolorizes from brown to colorless. A decolorization indicates an addition reaction has occurred, confirming the presence of a double bond.

Question 2: Identify a safety precaution that should be taken when working with bromine water in addition reactions.

Answer: Wear protective gloves and goggles to prevent skin and eye contact, as bromine water is toxic and corrosive.

Question 1: A commercial process uses hydrogen addition to convert unsaturated fats into saturated fats. Explain how addition reactions are utilized in this process and why.

Answer: Hydrogen addition reactions are used to break double bonds in unsaturated fats, adding hydrogen atoms across the double bonds. This process, called hydrogenation, converts liquid oils into solid fats, which are more stable and have a longer shelf life, commonly used in food industry.

Question 2: In the context of polymer production, how are addition reactions involved?

Answer: Addition reactions polymerize alkenes by linking many monomer units through the double bonds, forming long-chain polymers used in plastics.

Question 1: Explain the difference between addition of hydrogen (hydrogenation) and addition of halogens (halogenation) to alkenes. Include reaction conditions and products.

Answer: Hydrogenation involves adding hydrogen (H₂) across the double bond in the presence of a catalyst like nickel, producing a saturated alkane. Halogenation involves adding halogens like Br₂ or Cl₂, usually in the dark or with a solvent, forming a dihalogenated alkane. Both are addition reactions but differ in reagents, conditions, and products.

Question 2: Describe the role of electrophiles in addition reactions with alkenes.

Answer: Electrophiles are positively charged or electron-deficient species that attack the electron-rich double bond in alkenes, initiating the addition process.