Question

An iron nail was immersed in a solution of copper sulfate and when it was removed from the solution, it was coated with a layer of copper metal. Hereafter a different iron nail was immersed in a solution of zinc nitrate and removed this nail rusted? (con)
Just as rapidly as a new iron nail. Rank these three metals in order of activity from most active to least active.
A.Fe>Cu>Zn
B.Zn>Fe>Cu
C.Cu>Fe>Zn
D.Zn>Cu>Fe

Answer 1

Hint: the most reactive metal displaces the least reactive metal. When the iron nail is removed it is coated with a copper layer this means that the iron is more reactive than copper. Iron nail when immersed in the zinc solution, it came out as rusted this is possible when the solution is reactive than the nail.

Complete answer:
The main concept to solve this problem is that the most reactive metal displaces the least reactive metal. Now using this concept let us solve this question.
In the first part it says that when the iron nail was immersed in a solution of copper sulfate, it was coated with the layer of copper metal after removing. This means that iron was capable of reducing and displacing copper ions in the \[CuS{O_4}\] solution indicating that \[Fe\] is more reactive than Cu. This can also be understood with the simple reaction:
\[Fe(s) + CuS{O_4}\xrightarrow{{}}Cu(s) + FeS{O_4}(aq)\]
Now, for the second nail, we cannot say that the reaction is the same as that of the first nail. Let's assume that iron \[Fe\] is more reactive than \[Zn\] such that it is capable of replacing zinc \[Zn\] from its solution. Immersing the iron nail in the \[Zn{(N{O_3})_2}\;\] solution will coat it with a layer of metallic\[Zn\]. Coating \[Fe\] with a layer of less reactive metal would hinder its oxidation. By this assumption, coating \[Zn\] would make the iron nail not as susceptible to rusting as a nail with no coating. However, the observation that the two nails rust at the same rate disagrees with the assumption meaning that \[Fe\] is less reactive than\[Zn\]. Thus we can say that \[Zn > Fe\], and from the first part \[Fe > Cu\].
Hence ,\[Zn > Fe > Cu\]

Therefore the correct option is B.

Note:
What will make a metal more reactive depends upon the number of electrons in the outermost shell of an atom. Alkali metals are highly reactive because they readily lose the single electron in their outermost shell. To find out which metal is most reactive we will have to look into the reactivity series. This series of metals is based on their reactivity from highest to lowest.