Combustion and fuelsIB MYP Chemistry: Subtopic test

1. 1
   A family in Istanbul cooks on a gas hob that burns methane (natural gas). The flame is normally blue. One evening the flame turns yellow and black soot appears on the bottom of the pans. An engineer finds that the air holes of the burner are blocked.

   (a)

   Which pair are the products of the complete combustion of methane?

   [1 mark]

   • ACarbon monoxide and water
   • BCarbon and water
   • CCarbon dioxide and hydrogen
   • DCarbon dioxide and water

   (b)

   Which gas made by the blocked burner is toxic and has no smell?

   [1 mark]

   • ACarbon monoxide
   • BCarbon dioxide
   • CWater vapour
   • DNitrogen

   (c)

   Explain why the flame turned yellow and left black soot on the pans.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Lagos investigates the products made when ethanol burns in a spirit burner. She uses a pump to draw the waste gases through a U-tube surrounded by ice, and then bubbles the remaining gas through limewater. A colourless liquid collects in the U-tube and the limewater turns cloudy.

   (a)

   Which product does the cloudy limewater show is present?

   [1 mark]

   • AOxygen
   • BCarbon dioxide
   • CHydrogen
   • DCarbon monoxide

   (b)

   Why is the U-tube surrounded by ice?

   [1 mark]

   • ATo stop the ethanol burning
   • BTo freeze the carbon dioxide
   • CTo cool the gases so that water vapour condenses into a liquid
   • DTo make the limewater turn cloudy

   (c)

   Write the word equation for the complete combustion of ethanol.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Crude oil and natural gas are fossil fuels. They are found under the seabed in countries such as Norway and are burned in power stations, vehicles and homes.

   (a)

   Describe how crude oil and natural gas were formed.

   [3 marks]

   (b)

   Explain why fossil fuels are described as non-renewable, and why burning them increases the carbon dioxide in the atmosphere.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A charity in Nairobi wants to replace open wood fires in poorly ventilated kitchens with gas stoves. Wood fires burn with a smoky, yellow flame. Gas stoves burn with a controlled blue flame, but families would have to pay for gas cylinders, and leaking gas can cause fires. Gas is a fossil fuel.

   (a)

   Discuss the benefits and drawbacks of replacing open wood fires with gas stoves, and reach a justified conclusion.

   [6 marks]

   (b)

   A teacher shows a class how air supply affects combustion using a Bunsen burner. Design an investigation to show that restricting the air supply leads to incomplete combustion. Include a hypothesis with a scientific reason, the variables and a safety precaution.

   [6 marks]

   Total for question 4: 12 marks

End of questions