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Pieces of zinc react with copper sulfate solution - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2019 - Paper 1
Question 5
Pieces of zinc react with copper sulfate solution. Zinc sulfate solution is colourless. Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) (a) Describe what you would see when ... show full transcript
Worked Solution & Example Answer:Pieces of zinc react with copper sulfate solution - Edexcel - GCSE Chemistry Combined Science - Question 5 - 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 an excess of zinc is added to copper sulfate solution, initially, the blue color of the copper sulfate solution fades, indicating that copper(II) ions are reacting with zinc. As the reaction proceeds, zinc displaces the copper ions in the solution, and solid copper begins to form. You would see a color change from blue to colorless, and brownish-red copper solid precipitating at the bottom of the container.
Step 2
Explain, in terms of electrons, which particles have been oxidised and which particles have been reduced in this reaction.
Answer
In this redox reaction, zinc (Zn) is oxidised as it loses electrons:
ightarrow ext{Zn}^{2+} + 2 ext{e}^{-}$$ Copper (Cu^{2+}) is reduced as it gains electrons: $$ ext{Cu}^{2+} + 2 ext{e}^{-} ightarrow ext{Cu}$$ Thus, zinc is the reducing agent as it provides electrons, and copper(II) ions are the oxidising agent as they accept electrons.