Question

# What does Zn displace from ${\text{CuS}}{{\text{O}}_4}$ solution?

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Hint: Here, we will proceed by discussing the reactivity series along with its order. Then, we will discuss the displacement reactions and the process which they undergo. Finally, we will write down what happens when Zn is placed in ${\text{CuS}}{{\text{O}}_4}$ solution.

The reactivity series lists metals from the most reactive to the least reactive. A metal can displace a less reactive metal from its compounds. This is useful for extracting metals from their oxides.
Displacement reactions involve a metal and a compound of a different metal. In a displacement reaction, a more reactive metal will displace a less reactive metal from its compounds.
Displacement reactions are easily seen when a salt of the less reactive metal is in the solution. When a more reactive metal is dipped into the solution of the less reactive metal, the more reactive metal gradually disappears as it forms a solution and the less reactive metal coats the surface of the more reactive metal during the reaction.
The general chemical reaction involved here can be given as
More reactive metal + Solution of less reactive metal $\to$ Solution of more reactive metal + Less reactive metal.
The order of reactivity series (metals) is given as under
K > Na > Ba > Ca > Mg > Al > Mn > Zn > Fe > Ni > Sn > Pb > Cu > Ag
From the above series, we can say that the most reactive metal is potassium (i.e., it can displace any metal given in the above series from its solution) and the least reactive metal is silver (i.e., it cannot displace any metal given in the above series from its solution).
Clearly, from the reactivity series we can see that zinc (Zn) is more reactive than copper (Cu) which means that Zinc can displace Cu from its solution (${\text{CuS}}{{\text{O}}_4}$).
The reaction involved will be given by

Zn + ${\text{CuS}}{{\text{O}}_4}$ $\to$ ${\text{ZnS}}{{\text{O}}_4}$ + Cu
Therefore, Zn displaces Cu from ${\text{CuS}}{{\text{O}}_4}$.

Note: However, usually we will not have an activity series provided, but you have a table of standard reduction potentials. Then, we will use the table of standard reduction potentials to determine whether a reaction will occur when a piece of metal is placed in an aqueous solution containing ions of a different metal (i.e. in a solution of different metal).