Gases in the Atmosphere
6 marks · NormalThis question is about the properties of oxides and the production of carbon dioxide from metal carbonates.
Copper(II) carbonate is a green solid. When it is heated, a black solid and a gas are formed.
State the type of oxide produced and give one property that supports your answer.
Write a chemical equation for the thermal decomposition of copper(II) carbonate, using symbols.
The gas produced in this reaction is released to the atmosphere. Describe one environmental effect of increased carbon dioxide levels.
Calcium oxide formed from heating calcium carbonate is placed in water.
What is the nature of the solution formed and how does it relate to the type of oxide?
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.
Show answer
(a) — · must show black solid is copper(II) oxide, type: basic oxide; property such as turns red litmus blue or reacts with acid
(b) CuCO3(s) -> CuO(s) + CO2(g) · must show correct balanced equation with states
(c) Can cause global warming or climate change due to enhanced greenhouse effect · must show link between CO2 and greenhouse/global warming
(d) — · must show solution is alkaline/basic, because calcium oxide is a basic oxide and forms an alkaline solution in water
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States copper(II) oxide is a basic oxide.
B2 (a) · 1 mark · Supports with a property (e.g., reacts with acid, forms alkali in water, turns litmus blue).
A1 (b) · 1 mark · Correct balanced equation: CuCO₃(s) → CuO(s) + CO₂(g).
B3 (c) · 1 mark · Describes environmental effect of CO₂ (e.g., causes/can lead to global warming or climate change through greenhouse effect).
B4 (d) · 1 mark · States solution is alkaline/basic.
B5 (d) · 1 mark · Links to property of basic oxide (forms alkaline solution in water).
Worked solution
a) The black solid is copper(II) oxide, which is a basic oxide. One property supporting this is that copper(II) oxide reacts with acids to form salts and water, or it can turn red litmus paper blue.
b) The balanced equation is: CuCO₃(s) → CuO(s) + CO₂(g)
c) Increased carbon dioxide in the atmosphere can lead to the greenhouse effect, causing global warming and climate change.
d) When calcium oxide (a basic oxide) is added to water, the solution formed is alkaline. This is because basic oxides react with water (if soluble) to form alkalis (e.g., CaO + H₂O → Ca(OH)₂), showing that it is a basic oxide.