Question

Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of Aluminium are added to each solution. After some time, a change will be observed in:
A. I and II
B. II and III
C. III and I
D. All the three

Answer 1

We know very well that according to electrochemical series a more reactive element placed at the top can easily displace a less reactive element placed at bottom from their salt solution and the reactivity of the element is directly related to its oxidation and reduction potentials.

Complete step by step solution:
As we know from the electrochemical series that Aluminium is more reactive than copper, iron and zinc then comes zinc which is more reactive than iron and copper and next is iron which is more reactive than copper. We also know that more reactive elements can easily displace the less reactive elements from their salt solution. More reactive elements have the tendency to lose electrons resulting in a positive ion.
Similarly aluminium being most reactive among all will easily displace copper, zinc and iron from their respective solutions which result in precipitation of these elements at the bottom. The chemical equation of the same is as follows:
In the case of option A, when copper sulphate reacts with aluminium when considered the reaction would happen as shown below in the given chemical equation:
I. $2Al + 3CuS{O_4} \to 3Cu + A{l_2}{(S{O_4})_3}$
In the case of option B when iron sulphate reacts with aluminium when considered the reaction would happen as shown below in the given chemical equation:
II. $2Al + 3FeS{O_4} \to 3Fe + A{l_2}{(S{O_4})_3}$
In the case of option C when zinc sulphate reacts with aluminium when considered the reaction would happen as shown below in the given chemical equation:
III. $2Al + 3ZnS{O_4} \to 3Zn + A{l_2}{(S{O_4})_3}$
Resulting in all the three reacting with aluminium.

Therefore, the correct answer is (D).

Note: Reactivity of metals decreases down the electrochemical series as the oxidation potential decreases and the reactivity increases when the reduction increases. Thus, zinc sulphate is stored in copper containers but copper sulphate is not stored in zinc containers.