As fuels
4 marks · NormalThis question is about combustion of hydrocarbons and pollution.
Name the two conditions necessary for the complete combustion of a hydrocarbon.
Write the balanced word equation for the incomplete combustion of methane, producing carbon monoxide as one of the products.
Explain why carbon monoxide is produced during incomplete combustion and state one environmental or health effect it can cause.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Plenty of oxygen and ignition/heat · must show oxygen, heat/ignition
(b) methane + oxygen → carbon monoxide + water · must show methane, oxygen, carbon monoxide, water
(c) Carbon monoxide forms when there is not enough oxygen for complete combustion. It is dangerous because it is poisonous and prevents the blood from carrying oxygen, which can cause health problems like suffocation. · must show not enough oxygen, carbon monoxide, health/environmental effect
Also accept: complete combustion: sufficient oxygen, ignition/heat/air; balanced word equation: methane + oxygen → carbon monoxide + water
Common mistakes: omitting the word 'water' as a product in b); not mentioning oxygen shortage in c)
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Names both required conditions for complete combustion (enough oxygen and ignition/heat/air).
B2 (b) · 1 mark · Correct balanced word equation with all reactants and products (methane + oxygen → carbon monoxide + water).
M1 (c) · 1 mark · Recognises incomplete combustion occurs when not enough oxygen is supplied.
A1 (c) · 1 mark · States a valid risk/effect of carbon monoxide (e.g. poisonous; stops oxygen being carried; can cause suffocation or death).
Worked solution
a) The two conditions are: plenty of oxygen and heat/ignition.
b) Methane + oxygen → carbon monoxide + water
c) If there is not enough oxygen, incomplete combustion occurs, producing carbon monoxide, which is poisonous and reduces the blood's ability to transport oxygen. This can cause suffocation or be fatal.