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

1 Answer
Jun 11, 2018

b) #"Zn" > "Fe" > "Cu"#


Reactive metals displace unreactive metal ions from their solutions.

Iron in the first nail was capable of reducing and displacing copper ions in the #"Cu" "SO"_4# solution indicating that #"Fe"# is more reactive than #"Cu"#.

#ul("Fe" (s)) + "CuSO"_4 to ul("Cu"(s)) + "FeSO"_4(aq)#

What's going on with the second nail might not be as evident as the first one. Let's start with an assumption: assuming that iron #"Fe"# is more reactive than zinc such that it is capable of replacing zinc #"Zn"# from its solution.

Immersing the iron nail in the #"Zn"("NO"_3)_2# solution will coat it with a layer of metallic zinc. Coating iron, a metal that rusts- or gets oxidized- rapidly in humid air, with a layer of less reactive metal would hinder its oxidation. By this assumption, coating zinc would make the iron nail not as suspectable 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 iron is less reactive than zinc. Thus