In a displacement reaction, if Zinc is added to a Copper Sulphate solution, what is the observation?

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The correct answer is Option A: The blue colour of the solution fades and a reddish-brown deposit forms. When zinc is added to copper sulphate solution, a single displacement reaction occurs. Zinc displaces copper from the solution because it is more reactive, leading to the formation of zinc sulphate and the liberation of copper metal.

Step-by-Step Solution & Concepts:
When zinc is added to copper sulphate solution, a single displacement reaction occurs. Zinc displaces copper from the solution because it is more reactive, leading to the formation of zinc sulphate and the liberation of copper metal.

Working Principle: The reaction proceeds based on the reactivity series of metals, where zinc is placed higher than copper. Being more electropositive, zinc reduces copper ions ($Cu^{2+}$) to metallic copper while itself being oxidized to zinc ions ($Zn^{2+}$). The original blue colour is due to $Cu^{2+}$ ions, which fades as these ions are converted into non-colored $Zn^{2+}$ ions in the aqueous solution.

Key Formulas: $Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)$ — The chemical equation for the displacement reaction.; $Zn \rightarrow Zn^{2+} + 2e^-$ — The oxidation half-reaction.; $Cu^{2+} + 2e^- \rightarrow Cu$ — The reduction half-reaction.

Key Points: Zinc is more reactive than copper.; Copper sulphate solution is inherently blue due to $Cu^{2+}$ ions.; The reddish-brown deposit is solid metallic copper.; This reaction demonstrates the principles of redox (reduction-oxidation).

Advantages: Used in the extraction of metals.; Demonstrates the electrochemical reactivity series.

Disadvantages: Exothermic reactions can lead to safety hazards if not handled in controlled quantities.

Applications: Galvanization and metallurgical processes.; Basic chemical education labs.

Additional Info: Copper sulphate exists as a blue pentahydrate $CuSO_4 \cdot 5H_2O$ in crystal form.. Option B is wrong because green colour is usually associated with iron salts ($Fe^{2+}$). Option C is incorrect as the reaction occurs spontaneously. Option D is wrong because no hydrogen gas or other gases are evolved in this specific reaction.

Answer: A is correct — The more reactive zinc displaces copper from the blue copper sulphate solution, forming colourless zinc sulphate and reddish-brown copper metal.

Exam Tip: Remember the mnemonic 'Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold' to memorize the Reactivity Series effectively.

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Option B: The solution turns green

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Option C: No reaction occurs

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Option D: A gas is evolved

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