Energy resources and sustainabilityIB MYP Chemistry: Subtopic test

1. 1
   A city bus company in Japan is trialling buses that run on hydrogen. The hydrogen is made by electrolysis of water, using electricity from an offshore wind farm. The only substance released from the bus exhausts is water vapour.

   (a)

   Which of these is a renewable energy resource?

   [1 mark]

   • ANatural gas
   • BCoal
   • CWind
   • DCrude oil

   (b)

   Which statement about hydrogen as a fuel is correct?

   [1 mark]

   • AIt produces no carbon dioxide when it reacts with oxygen
   • BIt is a fossil fuel found in oil wells
   • CIt is easy to store as a dense liquid at room temperature
   • DIt releases less energy per gram than petrol

   (c)

   Outline two disadvantages of using hydrogen as a fuel for buses.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Students in São Paulo, Brazil, compare two fuels for cars. Ethanol is made by fermenting sugar from sugar cane. Petrol contains octane, which comes from crude oil. The students use this data: burning one mole of ethanol releases 1367 kJ and its relative molecular mass is 46; burning one mole of octane releases 5470 kJ and its relative molecular mass is 114.

   (a)

   What is the energy released per gram of ethanol, to 3 significant figures?

   [1 mark]

   • A0.0337 kJ g⁻¹
   • B29.7 kJ g⁻¹
   • C1321 kJ g⁻¹
   • D62 900 kJ g⁻¹

   (b)

   Why is ethanol made from sugar cane described as a biofuel?

   [1 mark]

   • AIt is made from crude oil by fractional distillation
   • BIt is made by splitting uranium nuclei
   • CIt releases more energy per gram than petrol
   • DIt is made from plant material that grew recently

   (c)

   Calculate the energy released per gram of octane and state which fuel releases more energy per gram.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A school science club in Kenya investigates which liquid fuel releases more energy per gram. They burn ethanol and then paraffin in a spirit burner under a metal can containing 100 g of water. They record the starting and final water temperatures and the mass of fuel burned. Results: ethanol, temperature rise 18.0 °C, mass burned 1.50 g; paraffin, temperature rise 30.0 °C, mass burned 1.40 g. The specific heat capacity of water is 4.2 J g⁻¹ °C⁻¹.

   (a)

   Identify the independent variable, the dependent variable and one control variable in the club's investigation.

   [3 marks]

   (b)

   Calculate the energy transferred to the water per gram of each fuel burned, in kJ g⁻¹. The accepted values for ethanol and paraffin are about 29.7 kJ g⁻¹ and 46 kJ g⁻¹. Suggest why the club's values are much lower and suggest one improvement to the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   The government of a sunny Gulf state is planning how to supply electricity and transport fuel up to 2050. At present it burns natural gas in power stations and petrol and diesel in vehicles. The options being considered are building a nuclear power station, building large solar farms, and growing oil palm plantations on cleared forest land to make biodiesel for transport. Some rural communities in neighbouring countries cannot afford any reliable electricity.

   (a)

   Discuss the advantages and disadvantages of building a nuclear power station for the electricity supply, and conclude whether the government should build one.

   [6 marks]

   (b)

   Evaluate the use of biodiesel from oil palm plantations on cleared forest land as a replacement for petrol and diesel, including who may lose out.

   [6 marks]

   Total for question 4: 12 marks

End of questions