Question 1: Define an alcohol in terms of its chemical structure.

Answer: An alcohol is an organic compound containing one or more hydroxyl (–OH) groups attached to a carbon atom.

Question 2: Describe the general mechanism by which alcohols are formed from alkenes.

Answer: Alcohols are formed from alkenes through hydration, where water adds across the double bond in the presence of an acid catalyst, following an electrophilic addition mechanism.

Question 3: Explain why alcohols are polar molecules.

Answer: Alcohols are polar because of the hydroxyl group (–OH), which contains a highly electronegative oxygen atom that creates a dipole, making the molecule polar.

Question 1: Calculate the molar mass of ethanol (C₂H₅OH).

Answer: 46 g/mol

Question 2: If 10 grams of ethanol undergo complete combustion, how many moles of CO₂ are produced? (Molar mass of CO₂ = 44 g/mol)

Answer: approximately 0.227 moles

Question 3: A sample contains 30 grams of methanol (CH₃OH). How many molecules are present? (Avogadro's number = 6.022 × 10²³ mol⁻¹)

Answer: approximately 1.21 × 10²⁴ molecules

Question 1: Outline the steps involved in safely preparing a sample of ethanol in a laboratory setting.

Answer: First, ensure the workspace is well-ventilated and safety equipment is worn. Measure the correct volume of ethanol using a pipette or measuring cylinder. Store in a labelled, sealed container away from heat sources. When handling, avoid spills and inhalation of vapours. Use appropriate PPE such as gloves and goggles throughout.

Question 2: Identify two safety precautions that must be taken when heating alcohols in the lab.

Answer: Use a water bath to heat alcohols gently and avoid open flames; ensure proper ventilation to prevent vapour build-up.

Question 1: A student burns 15 grams of methanol and produces 33 grams of carbon dioxide. Does this data support complete combustion? Explain your reasoning.

Answer: Yes, because complete combustion of methanol (CH₃OH) produces CO₂ and H₂O in a ratio consistent with the reaction. The molar mass of methanol is 32 g/mol, and combustion produces 1 mol of CO₂ (44 g). The data aligns with theoretical calculations indicating complete combustion.

Question 1: Describe the process of fermentation to produce ethanol, including the key raw materials, conditions, and chemical reactions involved. (6 marks)

Answer: Fermentation is a biological process where yeast converts sugars, such as glucose, into ethanol and carbon dioxide. The key raw materials are sugar-rich crops like barley, grapes, or sugarcane. Conditions include anaerobic environment, optimal temperature (~30°C), and pH control. The main reaction is C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂. The process involves enzymes like zymase facilitating the conversion.

Question 1: Explain how ethanol is used as a biofuel and discuss one advantage and one disadvantage of using ethanol in this way.

Answer: Ethanol is used as a biofuel by blending with petrol to power vehicles, reducing reliance on fossil fuels. An advantage is that it is renewable and reduces greenhouse gas emissions. A disadvantage is that it can cause corrosion in engines and may require more land for crop production, impacting food supply.