Question 1: Define a hydrogen fuel cell and explain how it produces electricity.

Answer: A hydrogen fuel cell is a device that converts chemical energy from hydrogen and oxygen into electrical energy through electrochemical reactions, producing water as a byproduct.

Question 2: Describe the chemical reaction that occurs in a hydrogen fuel cell when hydrogen reacts with oxygen.

Answer: Hydrogen reacts with oxygen to form water: 2H₂ + O₂ → 2H₂O.

Question 3: Explain why hydrogen is considered a clean fuel for use in fuel cells.

Answer: Because its only emission is water, making it environmentally friendly and producing no greenhouse gases.

Question 1: Calculate the volume of hydrogen gas (in litres) required to produce 10 kWh of electricity in a hydrogen fuel cell. Assume 1 mole of hydrogen produces 1.23 kWh of energy.

Answer: Approximately 8.13 litres of hydrogen gas. (Use the formula: volume = moles × molar volume at STP; 1 mol H₂ = 22.4 L)

Question 1: Identify two safety precautions that must be taken when handling hydrogen for fuel cell experiments.

Answer: Ensure proper ventilation to prevent accumulation of hydrogen gas, and avoid sparks or open flames due to hydrogen's flammability.

Question 2: Describe a simple safety procedure for storing hydrogen safely in a laboratory setting.

Answer: Store hydrogen in well-ventilated, leak-proof cylinders away from heat sources, and ensure cylinders are secured upright with proper regulators.

Question 1: A hydrogen fuel cell produces 50 kWh of electricity over 10 hours. If the efficiency of the fuel cell is 60%, what is the approximate amount of energy stored in hydrogen in kilowatt-hours? Show your working.

Answer: The energy stored in hydrogen = Energy output / efficiency = 50 kWh / 0.6 ≈ 83.33 kWh.

Question 1: Discuss the environmental advantages and disadvantages of using hydrogen fuel cells compared to traditional fossil fuels. (6 marks)

Answer: Advantages include zero emissions of greenhouse gases, water as a byproduct, and renewable potential. Disadvantages involve challenges in hydrogen production, storage difficulties, high costs, and safety concerns due to flammability.

Question 2: Explain how the electrochemical reaction in a hydrogen fuel cell generates electrical current.

Answer: Hydrogen molecules are split into protons and electrons at the anode. Electrons flow through an external circuit, creating current, while protons pass through an electrolyte to the cathode, where they combine with oxygen to form water.

Question 1: Name a modern application of hydrogen fuel cells in industry or transportation, and briefly describe its advantage.

Answer: Hydrogen fuel cells are used in some hydrogen-powered cars, providing a clean and quiet alternative to petrol engines with the benefit of zero tailpipe emissions.

Question 2: Suggest a potential future development in hydrogen fuel cell technology that could improve its practicality.

Answer: Developing more efficient and cost-effective methods of producing, storing, and distributing hydrogen to make fuel cells more accessible and economical.