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Pieces of zinc react with copper sulfate solution - Edexcel - GCSE Chemistry - Question 8 - 2019 - Paper 1
Question 8
Pieces of zinc react with copper sulfate solution. Zinc sulfate solution is colourless. (a) Describe what you would see when an excess of zinc is added to copper su... show full transcript
Worked Solution & Example Answer:Pieces of zinc react with copper sulfate solution - Edexcel - GCSE Chemistry - Question 8 - 2019 - Paper 1
Step 1
Describe what you would see when an excess of zinc is added to copper sulfate solution and the mixture left until the reaction is complete.
Answer
When excess zinc is added to the colourless copper sulfate solution, several visual changes can be observed:
- Colour Change: The initially blue solution of copper sulfate will gradually lose its colour.
- Solid Formation: A reddish-brown solid (copper) will begin to form and settle at the bottom of the container as the reaction proceeds.
- Disappearance of Solution: The blue copper sulfate solution will eventually turn colourless as the reaction reaches completion.
Step 2
Explain, in terms of electrons, which particles have been oxidised and which particles have been reduced in this reaction.
Answer
This reaction can be described as a redox reaction where the following changes occur:
-
Zinc Oxidation: Zinc (Zn) loses electrons during the reaction, resulting in the formation of zinc ions (Zn²⁺). This process can be represented by the half-equation:
ightarrow ext{Zn}^{2+}(aq) + 2 ext{e}^-$$
Here, zinc is said to be oxidised as it loses electrons.
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Copper Reduction: Copper ions (Cu²⁺) in the solution gain the electrons lost by zinc, resulting in the formation of solid copper (Cu). This process can be represented by the half-equation:
ightarrow ext{Cu}(s)$$
In this case, copper is reduced because it gains electrons.