Question 1: Define combustion in terms of hydrocarbon reactions.

Answer: Combustion is a chemical reaction where a hydrocarbon reacts with oxygen to produce carbon dioxide, water, and energy.

Question 2: Describe the main products formed when a hydrocarbon undergoes complete combustion.

Answer: The main products are carbon dioxide (CO₂) and water (H₂O).

Question 3: Explain why incomplete combustion produces carbon monoxide instead of carbon dioxide.

Answer: Incomplete combustion occurs when there is insufficient oxygen, leading to the formation of carbon monoxide (CO) instead of carbon dioxide (CO₂).

Question 1: Calculate the amount of energy released when 1 mole of methane (CH₄) undergoes complete combustion. The enthalpy change of combustion is -890 kJ/mol.

Answer: 890 kJ

Question 2: If 2.5 litres of propane (C₃H₈) are combusted at room temperature and pressure, calculate the energy released. (Molar volume of gas = 24 dm³/mol). Use enthalpy of combustion = -2220 kJ/mol.

Answer: Approximately 231.75 kJ

Question 1: Identify three safety precautions that should be taken during a combustion experiment involving hydrocarbons.

Answer: Use proper protective equipment, conduct the experiment in a well-ventilated area, and keep flammable materials away from the flame.

Question 2: Describe a typical setup for safely burning a hydrocarbon sample in a laboratory.

Answer: A typical setup includes a secure stand with a Bunsen burner connected to a gas supply, a heat-resistant mat, safety goggles, and a fire extinguisher nearby. The experiment should be conducted in a fume cupboard or well-ventilated area.

Question 1: A sample of hydrocarbon releases 500 kJ of energy when burned. The sample is known to be C₄H₁₀ (butane). Given that the enthalpy of combustion for butane is -2877 kJ/mol, estimate the number of moles in the sample.

Answer: Approximately 0.174 mol

Question 2: A combustion process produces a higher proportion of carbon monoxide than carbon dioxide. What does this suggest about the oxygen supply during combustion?

Answer: It suggests that oxygen supply was insufficient, leading to incomplete combustion.

Question 1: Explain how understanding combustion is important for reducing pollution from vehicle engines.

Answer: By understanding combustion, engineers can optimise fuel efficiency and develop technologies like catalytic converters to reduce emissions of pollutants such as CO and unburned hydrocarbons.

Question 2: Describe one technological advancement that has improved combustion efficiency in power plants.

Answer: The use of supercritical boilers and flue gas desulphurisation systems has improved combustion efficiency and reduced pollutant emissions in power plants.