Why does colour of copper sulphate solution change when an iron nail is dipped in it?

Question

Answer

Due to the Displacement Reaction, Copper in the Copper Sulphate solution collects over Iron. So, the colour of Copper Sulphate solution fades.

Answer

When an iron nail immersed in the solution of copper sulphate than iron displaces copper from the solution of copper sulphate because iron is more reactive than copper. Therefore copper sulphate solution colour changes from blue to pale green.

Answer

Introduction
Copper sulphate is an inorganic compound with the chemical formula CuSO4. It is a blue crystalline substance that dissolves in water to give a blue solution. When an iron nail is dipped into copper sulphate solution, the colour of the solution changes from blue to green.

Explanation
The colour change occurs due to the following reasons:

Redox Reaction: When the iron nail is dipped into the copper sulphate solution, a redox reaction takes place. The iron atom loses electrons and gets oxidized to form Fe2+ ions. The copper ion in the copper sulphate gains electrons and gets reduced to form copper atoms. This reaction is represented as follows:
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

Formation of Iron Sulphate: The iron atom reacts with the sulphate ion present in the copper sulphate solution to form iron sulphate. This reaction is represented as follows:
FeSO4(aq) + CuSO4(aq) → FeSO4(aq) + CuSO4(aq)

Formation of Copper: The copper ion present in the copper sulphate solution gains electrons and gets reduced to form copper atoms. These copper atoms get deposited on the surface of the iron nail, giving it a reddish-brown colour. This reaction is represented as follows:
Cu2+(aq) + 2e- → Cu(s)

Formation of Iron Oxide: As the iron nail gets oxidized, it reacts with oxygen present in the air to form iron oxide. This iron oxide gets deposited on the surface of the iron nail, giving it a reddish-brown colour. This reaction is represented as follows:
4Fe(s) + 3O2(g) → 2Fe2O3(s)

Colour Change: The green colour of the copper sulphate solution is due to the presence of copper ions. As the copper ions get reduced and deposited on the surface of the iron nail, the concentration of copper ions in the solution decreases, leading to a change in the colour of the solution from blue to green.

Conclusion
In conclusion, the colour of copper sulphate solution changes from blue to green when an iron nail is dipped in it due to the redox reaction between iron and copper ions, formation of iron sulphate and iron oxide, deposition of copper on the surface of the iron nail, and decrease in the concentration of copper ions in the solution.

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