1. 1
   A city environmental agency is monitoring air quality near a busy road. Sensors record levels of several gases, including carbon monoxide and oxides of nitrogen, which are both produced by car engines.

   (a)

   Which two gases make up approximately 99% of clean, dry air?

   [1 mark]

   • ANitrogen and oxygen
   • BNitrogen and carbon dioxide
   • COxygen and carbon dioxide
   • DNitrogen and hydrogen

   (b)

   Why does incomplete combustion in car engines produce carbon monoxide instead of carbon dioxide?

   [1 mark]

   • AThe engine temperature is too low for any reaction to occur
   • BThere is too much oxygen present
   • CThe fuel contains no carbon
   • DThere is insufficient oxygen for complete combustion

   (c)

   (i) State how oxides of nitrogen are formed in a car engine. (ii) State one adverse effect on health or the environment caused by oxides of nitrogen.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A historic coal-fired power station has been burning coal containing sulfur compounds for many decades. Local records show that nearby forests and lakes have been damaged over this time, and engineers are now considering flue gas desulfurisation using calcium oxide to reduce emissions.

   (a)

   Which gas released by a coal-fired power station is the main cause of acid rain?

   [1 mark]

   • ANitrogen
   • BSulfur dioxide
   • COxygen
   • DArgon

   (b)

   Why is calcium oxide used in flue gas desulfurisation at the power station?

   [1 mark]

   • AIt converts carbon dioxide into oxygen
   • BIt increases the amount of sulfur dioxide released
   • CIt reacts with and removes sulfur dioxide from the flue gases
   • DIt removes nitrogen from the air

   (c)

   Suggest two other strategies, besides flue gas desulfurisation, that could be used to reduce sulfur dioxide emissions or the harm caused by acid rain from power stations of this type.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A tropical rainforest region is being studied because large areas of trees are being cut down and burned to clear land for cattle farming. Scientists are concerned this is contributing to increased levels of greenhouse gases and reducing the rate of photosynthesis in the region.

   (a)

   Scientists are concerned this is contributing to increased levels of greenhouse gases. (a) Name two greenhouse gases linked to this deforestation and cattle farming, and state the source of each. (b) Explain how these greenhouse gases contribute to global warming.

   [3 marks]

   (b)

   (a) Write the word equation and the balanced symbol equation for photosynthesis. (b) Explain why cutting down and burning large areas of forest, as described, is likely to increase the rate of global warming.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A national government is designing a strategy to reduce the country's contribution to climate change and acid rain over the next twenty years. Advisors have presented data on emissions from vehicles, power stations, farming and deforestation.

   (a)

   Explain, with reference to the sources of carbon dioxide, methane, oxides of nitrogen and sulfur dioxide, why each of these gases contributes to climate change or acid rain, and describe strategies the government could use to reduce each problem.

   [6 marks]

   (b)

   Catalytic converters are fitted to reduce pollution from cars. Explain how a catalytic converter removes carbon monoxide and oxides of nitrogen from car exhaust gases, and discuss why this technology alone may not be enough to solve the country's wider air quality and climate problems.

   [6 marks]

   Total for question 4: 12 marks

End of questions