1. 1
   A power station burns a fossil fuel containing carbon, hydrogen and a small amount of sulfur, and scientists monitor the gases released from its chimney.

   (a)

   A power station burns a fossil fuel that contains a small amount of sulfur as an impurity. Which gas released during combustion is mainly responsible for causing acid rain?

   [1 mark]

   • ACarbon dioxide
   • BSulfur dioxide
   • CWater vapour
   • DNitrogen gas

   (b)

   Which gas is produced when combustion of the fuel is incomplete due to a limited oxygen supply?

   [1 mark]

   • ACarbon monoxide
   • BOxygen
   • CWater vapour only
   • DSulfur dioxide only

   (c)

   State the elements present in this fuel, and name the gas produced from the sulfur impurity when the fuel burns.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An engineer tests the same fuel under two conditions: burning in a plentiful oxygen supply, and burning in a limited oxygen supply.

   (a)

   A fuel burns completely in a plentiful supply of oxygen. Which two products are formed?

   [1 mark]

   • ACarbon monoxide and water vapour
   • BSoot (carbon) and oxygen
   • CCarbon dioxide and water vapour
   • DSulfur dioxide and hydrogen

   (b)

   The same fuel is burned in a limited oxygen supply. Which products are most likely to form in addition to carbon dioxide and water?

   [1 mark]

   • AOnly water vapour
   • BOnly oxygen gas
   • COnly nitrogen gas
   • DCarbon monoxide and solid particles (soot)

   (c)

   Explain why incomplete combustion produces different products from complete combustion.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An environmental scientist investigates the atmospheric effects of gases and particles released when fossil fuels are burned in cities and power stations.

   (a)

   Explain how sulfur dioxide and oxides of nitrogen released from burning fuels lead to acid rain, and how carbon dioxide released from burning fuels is linked to climate change.

   [3 marks]

   (b)

   A fuel contains carbon, hydrogen and sulfur. State the products that would be released if this fuel underwent (i) complete combustion and (ii) incomplete combustion, relating each product to the elements present in the fuel.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A government environmental panel is preparing a report on the atmospheric impact of burning fossil fuels in industry and transport, and must explain how each combustion product affects the environment.

   (a)

   Explain the environmental effects of the different products released when fossil fuels containing carbon, hydrogen and sulfur are burned, including the effects of sulfur dioxide, oxides of nitrogen, carbon dioxide, and solid particles.

   [6 marks]

   (b)

   Explain the difference between complete and incomplete combustion of a fuel, and explain how the products formed can be used to determine whether combustion was complete or incomplete.

   [6 marks]

   Total for question 4: 12 marks

End of questions