Which of the following reactions are not feasible ?

Correct Answer: Zn + CaSO₄

Step-by-Step Explanation:

A single displacement reaction between a metal and a metal salt solution takes place only if the reacting metal is more reactive than the metal present in the salt solution. A more reactive metal can displace a less reactive metal from its salt solution.

To determine which reaction is not feasible, we refer to the reactivity series of metals (from most reactive to least reactive):

K > Ca > Na > Mg > Al > Zn > Fe > Pb > Cu

Let's analyze the feasibility of each given reaction based on the position of the metals in the reactivity series:

1. Al + CuSO₄:
Aluminium (Al) is higher up in the reactivity series than Copper (Cu). Therefore, aluminium is more reactive than copper and can easily displace copper from copper sulfate solution. This reaction is feasible:
2Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu

2. Mg + ZnSO₄:
Magnesium (Mg) is located above Zinc (Zn) in the reactivity series. Since magnesium is more reactive than zinc, it can displace zinc from zinc sulfate solution. This reaction is feasible:
Mg + ZnSO₄ → MgSO₄ + Zn

3. PbSO₄ + Fe:
Iron (Fe) is more reactive than Lead (Pb) as iron lies above lead in the reactivity series. Thus, iron can displace lead from lead sulfate solution. This reaction is feasible:
Fe + PbSO₄ → FeSO₄ + Pb

4. Zn + CaSO₄:
Zinc (Zn) is located below Calcium (Ca) in the reactivity series. This means zinc is less reactive than calcium, so it cannot displace calcium from calcium sulfate solution. Therefore, this reaction is not feasible (no reaction occurs):
Zn + CaSO₄ → No Reaction

Thus, the reaction that is not feasible is Zn + CaSO₄.