The metal used to recover copper from a solution of copper sulphate is?

Analysis

The question asks us to identify which metal can displace copper from a copper(II) sulphate solution. This is a classic question based on the Reactivity Series of Metals (also known as the Electrochemical Series).

Concept: The Reactivity Series

In chemistry, a more reactive metal can displace a less reactive metal from its salt solution. This is known as a displacement reaction.

The Reactivity Series ranks metals based on their tendency to lose electrons (their reducing power). The order of some common metals is: K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > (H) > Cu > Hg > Ag > Au

For a metal to displace copper from a copper(II) sulphate solution ($CuSO_4$), the metal must be higher in the reactivity series than copper.

Step-by-Step Solution

1. Analyze the options: • A. Na (Sodium): Sodium is very reactive and would react violently with the water in the solution rather than simply displacing the copper. It is not used for this purpose. • B. Ag (Silver): Silver is below copper in the reactivity series. It cannot displace copper. • C. Hg (Mercury): Mercury is also below copper in the reactivity series. It cannot displace copper. • D. Fe (Iron): Iron is above copper in the reactivity series. Therefore, iron can displace copper from its solution.

2. The Chemical Equation: When iron is added to copper(II) sulphate solution, the following reaction occurs: $$Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)$$ The iron dissolves to form iron(II) sulphate, and the copper is deposited as a solid.

Conclusion

Since iron is more reactive than copper, it effectively displaces copper from the copper sulphate solution.

Exam Tip

Remember the mnemonic for the reactivity series: "Please Stop Calling Me A Zebra In Large Heavy Cages, Save Gold." (Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold). Any metal to the left of another can displace it from its salt solution!