Reactivity of Metals

Different metals show different behaviours towards chemical reagents. Some metals are more reactive, while others are less reactive. The reactive metals can easily lose electrons to form positive ions. The relative reactivity of metals can be easily determined with the help of displacement reactions. In a displacement reaction, a more reactive metal displaces a less reactive metal from its salt solution.

Reactions of copper, zinc, iron and Aluminium with copper Sulphate solution:

Cu (s) + CuSO₄ (aq) → no reaction
Zn (s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu (s)
Fe (s) + CuSO₄ (aq) →FeSO₄ (aq) + Cu (s)
2Al (s) + 3CuSO₄ (aq) → Al₂ (SO₄)₃ + 3Cu (s)

Reactions of copper, zinc, iron and Aluminium with ferrous Sulphate solution:

Cu (s) + FeSO₄ (aq) → no reaction
Zn (s) + FeSO₄ (aq) → ZnSO₄ (aq) + Fe (s)
Fe (s) + FeSO₄ (aq) → no reaction
2Al (s) + 3FeSO₄ (aq) → Al₂ (SO₄)₃ + 3Fe (s)

Reactions of copper, zinc, iron and Aluminium with zinc Sulphate solution:

Cu (s) + ZnSO₄ (aq) → no reaction
Zn (s) + ZnSO₄ (aq) → no reaction
Fe (s) + ZnSO₄ (aq) → no reaction
2Al (s) + 3ZnSO₄ (aq) → Al₂(SO₄)₃ + 3Zn (s)

Reactions of copper, zinc, iron and Aluminium with Aluminium Sulphate solution:

Cu (s) + Al₂(SO₄)₃ (aq) → no reaction
Zn (s) + Al₂(SO₄)₃ (aq) → no reaction
Fe (s) + Al₂(SO₄)₃ (aq) → no reaction
Al (s) + Al₂(SO₄)₃ (aq) → no reaction

No reaction occurs when any of the metals from zinc, iron, Aluminium and copper is placed in an aqueous solution of Al₂(SO₄)₃.

Therefore, from the above, we can conclude the reactivity of elements in the following order-

Aluminium is more reactive than zinc.
Zinc is more reactive than iron.
Iron is more reactive than copper.

Hence, Aluminium is the most reactive, and copper is the least reactive metal.

This experiment aims to study the interaction of metals, such as zinc, iron, copper and Aluminium with their salt solutions and to arrange them according to their reactivity.

The apparatus and chemicals required for this experiment are:

Apparatus

Four beakers (100 mL)
Watch glass
One piece of sandpaper

Chemicals

Zinc metal strips
Copper metal strips
Aluminium metal strips
Iron metal strips
5% concentrated aqueous solution of zinc Sulphate
5% concentrated aqueous solution of copper Sulphate
5% concentrated aqueous solution of Aluminium Sulphate
5% concentrated aqueous solution of ferrous Sulphate

Experitment Procedure

The procedure followed for this experiment is as follows:

Take zinc, copper, iron and Aluminium metal strips and clean their surfaces with sandpaper.
Collect about 60 mL of the 5% concentrated solutions of zinc Sulphate, copper Sulphate, ferrous Sulphate and Aluminium Sulphate in different beakers labelled ‘A’, ‘B’, ‘C’ and ‘D’, respectively.
Take 4 clean strips of zinc metal and place one each in the beakers ‘A’, ‘B’, ‘C’ and ‘D’ containing different salt solutions.
Observe the changes in each of the beakers.
The beakers in which the colour of the solution changes or a metallic deposition is seen on the metal strip contain the salt solution of the metal, which is less reactive than zinc.
Repeat the above process with the other metal samples such as copper, iron and Aluminium.

Conclusion

Hence, it can be concluded that,

The action of Zn, Fe, Cu and Al metals is observed in salt solutions such as ZnSO₄, FeSO₄, CuSO₄ and Al₂(SO₄)₃.

It is observed that Al is able to displace Fe, Cu and Zn from their salt solutions; therefore, Al is most reactive compared to Fe, Cu and Zn.

Also, Cu is unable to displace any metal among Al, Fe and Zn from their salt solutions; therefore, Cu is the least reactive compared to Al, Fe and Zn.

Fe is unable to displace Zn from its salt solution, whereas Zn is able to displace Fe from its salt solution; therefore, Zn is more reactive than Fe.

Based on the above observations, the metals in decreasing order of reactivity are as follows:

Al> Zn> Fe> Cu

Let’s explore this through a simulation.

Q1. What is the order of reactivity of Al, Zn, Fe, Cu?

Answer: Al> Zn> Fe> Cu

Q2. How does potassium react with water?

Answer:Metals like potassium and sodium react violently with cold water. In the case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.

2K(s) + 2H2O(l) → 2KOH(aq) + H2 (g) + heat energy

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2 (g) + heat energy

Q3. Which gas is evolved when a metal reacts with acid?

Answer: Metals react with acids to evolve hydrogen gas.

Metal + Acid→ Salt +H2

Hydrogen gas is not evolved when a metal reacts with nitric acid. This is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2 ). But magnesium (Mg) and manganese (Mn) react with very dilute HNO3 to evolve H2 gas.