Question

Which displacement reaction will not occur among the following reactions?
A) ${ Zn+ } { CuSO }_{ 4 }$
B) ${ Fe+ } { CuSO }_{ 4 }$
C) ${ Cu+ } { FeSO }_{ 4 }$
D) ${ Mg+ } { CuSO }_{ 4 }$

Answer 1

Hint: A displacement reaction is where a more reactive metal displaces a less reactive metal from a compound. In other words, a metal higher up in the reactivity series will 'push out' a metal lower in the series.

Complete step-by-step answer:
The activity series (also known as reactivity series) of metals is a series in which metals are arranged in the decreasing order of reactivity. Thus the most reactive metal is placed at the top of the series while the least reactive metal is placed at the bottom of the series.
This series is prepared by performing displacement reactions between various metals and their salt solutions.

Visualization of Displacement reaction with an example

A) Zinc is higher up in the reactivity series than copper. So zinc reacts with the solution displacing copper to form ${ ZnSO }_{ 4 }$ and the Cu metal gets deposited over the rod. The ${ ZnSO }_{ 4 }$ solution is colorless and hence due to the formation of this solution the blue color starts fading. The following chemical reaction takes place;
${ Zn+CuSO }_{ 4 }{ \rightarrow Cu+ZnSO }_{ 4 }$

B) When iron reacts with copper sulfate solution a simple displacement reaction takes place to give Ferrous Sulphate and copper as products. The following chemical reaction takes place;
${ Fe+CuSO }_{ 4 }{ \rightarrow Cu+FeSO }_{ 4 }$

C) Iron is more reactive than copper therefore, in the reaction of iron sulfate with copper, iron will not be displaced. So, there would be no reaction in this case. Hence, no displacement reaction.

D) When Magnesium reacts with copper sulfate solution, magnesium sulfate and copper is formed. The following reaction can be written as;
${ Mg+CuSO }_{ 4 }{ \rightarrow Cu+MgSO }_{ 4 }$

Hence, the correct option is C.

Note: The possibility to make a mistake is that you may choose option D, But according to the reactivity series. Magnesium is more reactive than copper so it displaces copper metal.