CHEMISTRY QUESTION

Question

Nickel metal, Ni (s), was left in a solution of aluminum (III) ions (Al³⁺), iron (II) ions (Fe2⁺), and copper (II) ions (Cu²⁺). What reaction is most likely to be spontaneous? Write a balanced redox reaction equation for the reaction.

Answer 1

We need to look at the standard reduction potentials which can be found in a table in a text book or on the internet. The values I found are as follows:

Al³⁺ + 3e- ==> Al(s) ... Eº = -1.66 V

Fe²⁺ + 2e- ==> Fe(s) ... Eº = -0.44 V

Cu²⁺ + 2e- ==> Cu(s) ... Eº = +034 V

Ni²⁺ + 2e ==> Ni(s) ... Eº = -0.25 V

In a redox reaction, Ni(s) would be converted to Ni²⁺ by being oxidized and the other metal would have to be reduced. Since Cu²⁺ has the greatest reduction potential, it will be preferentially reduced and the following reaction will take place:

Ni(s) + Cu²⁺(aq) ==> Ni²⁺(aq) + Cu(s)

Reaction of Ni(s) with either Fe²⁺ or Al³⁺ would not be spontaneous as Ni²⁺ has a greater reduction potential than either of these 2 other metals.