Inorganic Chemistry
7 marks · EasyAnswer the questions about greenhouse gases and redox agents.
State what is meant by a 'greenhouse gas' and name one greenhouse gas present in the Earth’s atmosphere.
Explain how carbon dioxide is released into the atmosphere during the combustion of fossil fuels.
Describe one possible environmental impact caused by an increase in greenhouse gases such as carbon dioxide.
In the following reaction, identify the oxidising agent and explain your answer in terms of oxygen transfer: Mg(s) + CuO(s) → MgO(s) + Cu(s)
Suggest why carbon dioxide is not removed from the atmosphere as quickly as it is added by combustion.
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) A greenhouse gas absorbs infrared radiation and traps heat in the atmosphere. Examples: carbon dioxide, methane, water vapour.
(b) Combustion of fossil fuels releases carbon, which reacts with oxygen to form carbon dioxide.
(c) Rising sea levels, melting polar ice caps, or increased extreme weather.
(d) CuO is the oxidising agent because it provides oxygen to magnesium (Mg) and is itself reduced to copper (Cu).
(e) Because natural processes that remove CO2 (e.g., photosynthesis, dissolving in oceans) are slower than the rate of addition.
Common mistakes: Confusing oxidising and reducing agents; Naming oxygen as a greenhouse gas; Saying global warming is caused only by CO2, without mentioning other effects
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct definition of greenhouse gas
B2 (a) · 1 mark · Correct example named (e.g., carbon dioxide)
B3 (b) · 1 mark · Correct explanation of combustion releasing CO2
B4 (c) · 1 mark · One valid environmental impact identified
M1 (d) · 1 mark · Identification of CuO as oxidising agent
M2 (d) · 1 mark · Explanation using oxygen transfer (CuO provides oxygen/magnesium gains oxygen)
B5 (e) · 1 mark · Correct reason for slow removal (natural processes slower than addition)
Worked solution
a) A greenhouse gas is a gas that absorbs infrared radiation and helps trap heat in the Earth's atmosphere. An example is carbon dioxide (CO_2).
b) When fossil fuels burn, carbon in the fuel reacts with oxygen in the air to produce carbon dioxide.
c) One impact could be that global temperatures increase, causing glaciers to melt and sea levels to rise. Other effects include extreme weather events such as floods or droughts.
d) In Mg(s) + CuO(s) → MgO(s) + Cu(s), CuO is the oxidising agent because it gives oxygen to magnesium (Mg), causing magnesium to be oxidised to magnesium oxide (MgO). CuO is reduced to copper (Cu) as it loses oxygen.
e) Carbon dioxide is not removed from the atmosphere as quickly as it is added because processes like photosynthesis (by plants) and absorption by oceans are relatively slow compared to the large amount produced by human activities.