Question 1: Hydrogen fuel cells generate electricity through a chemical reaction between hydrogen and oxygen, producing only water as a by-product. Explain the basic mechanism of how a hydrogen fuel cell produces electrical energy.

Answer: Hydrogen gas is supplied to the anode where it is split into protons and electrons. The electrons flow through an external circuit, creating electricity. The protons pass through the electrolyte to the cathode, where they combine with oxygen and electrons to form water.

Question 1: Define a hydrogen fuel cell.

Answer: A device that converts hydrogen and oxygen into electricity through a chemical reaction, producing water as a by-product.

Question 2: What are the main advantages of using hydrogen fuel cells compared to traditional fossil fuels?

Answer: Hydrogen fuel cells produce only water as waste, have high efficiency, produce no greenhouse gases during operation, and can be refuelled quickly.

Question 1: Calculate the amount of energy (in kJ) produced when 2 mol of hydrogen gas undergoes complete reaction in a hydrogen fuel cell. (Use the standard enthalpy change for the reaction: ΔH = -285.8 kJ/mol H₂).

Answer: 571.6 kJ

Question 2: If a hydrogen fuel cell produces 0.5 kWh of electrical energy, how many moles of hydrogen are consumed? (Use the energy conversion: 1 kWh = 3600 kJ).

Answer: 0.5 kWh = 1800 kJ; moles of H₂ = 1800 / 285.8 ≈ 6.29 mol

Question 1: Describe a basic experimental setup to test the efficiency of a hydrogen fuel cell in a laboratory setting.

Answer: Set up a hydrogen gas supply connected to the anode of the fuel cell, connect an external circuit to measure current, connect the cathode to oxygen or air, and measure the voltage and current output to evaluate efficiency.

Question 2: Identify two variables that should be controlled in an experiment testing hydrogen fuel cell performance.

Answer: Temperature and hydrogen or oxygen gas purity.

Question 3: What safety precautions should be taken when handling hydrogen gas in a laboratory environment?

Answer: Use well-ventilated areas, avoid sources of ignition, handle with proper equipment, and ensure leak detection for hydrogen leaks.

Question 1: A hydrogen fuel cell produces a voltage of 0.8 V and a current of 2 A. Calculate the power output in watts.

Answer: Power = Voltage × Current = 0.8 V × 2 A = 1.6 W

Question 2: The efficiency of a hydrogen fuel cell is determined by comparing the electrical energy produced to the energy content of the hydrogen used. If 10 mol of hydrogen (enthalpy change of -285.8 kJ/mol) is used, and the electrical energy generated is 2500 kJ, what is the efficiency of the fuel cell? Express your answer as a percentage.

Answer: Total energy in hydrogen = 10 × 285.8 = 2858 kJ; Efficiency = (2500 / 2858) × 100 ≈ 87.4%

Question 1: Discuss the potential advantages and disadvantages of replacing petrol-powered vehicles with hydrogen fuel cell vehicles. Include environmental, economic, and technical considerations in your answer. (6 marks)

Answer: Advantages include zero emissions during operation, renewable hydrogen sources, and high efficiency. Disadvantages involve the current high cost of fuel cell technology, challenges in hydrogen storage and distribution, safety concerns due to hydrogen's flammability, and the need for infrastructure development.

Question 1: Describe how hydrogen fuel cells are used in the development of clean energy transport solutions, such as in buses or trains. Discuss the benefits and current limitations.

Answer: Hydrogen fuel cells are used in buses and trains to produce electricity for propulsion, offering zero emissions and quiet operation. Benefits include reduced air pollution and greenhouse gases. Limitations involve high costs, hydrogen storage challenges, and the need for dedicated refuelling infrastructure.