1. 1
   A city bus operator is trialling a fleet of buses powered by hydrogen-oxygen fuel cells instead of diesel engines, to reduce roadside emissions.

   (a)

   Which substance is produced as the only chemical product when the fuel cell operates?

   [1 mark]

   • ACarbon dioxide
   • BWater
   • CCarbon monoxide
   • DSulfur dioxide

   (b)

   Which pair of substances are supplied to the fuel cell to generate electricity in the bus?

   [1 mark]

   • AHydrogen and oxygen
   • BHydrogen and nitrogen
   • CDiesel and oxygen
   • DMethane and oxygen

   (c)

   Give two reasons why the bus operator might prefer hydrogen-oxygen fuel cell buses over diesel-engine buses.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A remote research station in Antarctica is considering replacing its petrol generators with hydrogen-oxygen fuel cells to supply electricity, since fuel deliveries are difficult in winter.

   (a)

   Compared with a petrol engine, what is a disadvantage of the fuel cell system for this research station?

   [1 mark]

   • AFuel cells produce toxic waste products
   • BFuel cells release large amounts of carbon dioxide
   • CFuel cells cannot generate electricity in cold climates
   • DHydrogen is difficult and costly to store and transport safely

   (b)

   Which statement correctly compares the two energy sources for the research station?

   [1 mark]

   • APetrol engines produce water as their only product, fuel cells produce carbon dioxide
   • BPetrol engines and fuel cells both require an ignition spark to release energy
   • CFuel cells produce electricity directly from a chemical reaction, petrol engines burn fuel to release heat that is converted to mechanical energy
   • DFuel cells require combustion of hydrogen in air to release energy

   (c)

   Suggest one practical difficulty the research station might face if it switches to hydrogen-oxygen fuel cells, other than the cost of hydrogen storage.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A car manufacturer is comparing a hydrogen-oxygen fuel cell vehicle with a conventional petrol vehicle for a government tender on low-emission transport.

   (a)

   State three differences between the two vehicles in terms of the substances released while driving.

   [3 marks]

   (b)

   Explain four factors the government should consider before awarding the tender to fuel cell vehicles rather than petrol vehicles, covering both advantages and disadvantages of hydrogen fuel cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A shipping company is deciding whether to convert its cargo ships from diesel engines to hydrogen-oxygen fuel cells to meet new international emissions targets.

   (a)

   Discuss the chemical advantages of making this switch, referring to the substances produced by each power source.

   [6 marks]

   (b)

   Discuss the practical disadvantages the shipping company would need to overcome before converting its ships to hydrogen-oxygen fuel cells.

   [6 marks]

   Total for question 4: 12 marks

End of questions