Identify the species oxidized, species reduced, and the oxidizing agent and reducing agent for all the reactions in the previous problem.

(a) \({\rm{Al}}(s) + {\rm{Z}}{{\rm{r}}^{4 + }}(aq) \to {\rm{A}}{{\rm{l}}^{3 + }}(aq) + {\rm{Zr}}(s)\)

(b) \({\rm{A}}{{\rm{g}}^ + }(aq) + {\rm{NO}}(g) \to {\rm{Ag}}(s) + {\rm{N}}{{\rm{O}}_3}^ - (aq)\)(acidic solution)

(c) \({\rm{Si}}{{\rm{O}}_3}^{2 - }(aq) + {\rm{Mg}}(s) \to {\rm{Si}}(s) + {\rm{Mg}}{({\rm{OH}})_2}(s)\)(basic solution)

(d) \({\rm{Cl}}{{\rm{O}}_3}^ - (aq) + {\rm{Mn}}{{\rm{O}}_2}(s) \to {\rm{C}}{{\rm{l}}^ - }(aq) + {\rm{Mn}}{{\rm{O}}_4}^ - (aq)\)(basic solution)

• The oxidation-reduction reaction is also known as aredox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.
• The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two half reactions, net total equation can be obtained. This method of balancing redox reaction is known ashalf equation method.

Al is getting oxidized so, act as reducing agent and \({\rm{Zr}}\) is getting reduced so, act as oxidizing agent.

Consider the following balanced reaction:

\(4{\rm{Al}}({\rm{s}}) + 3{\rm{Z}}{{\rm{r}}^{4 + }}(aq) \to 4{\rm{A}}{{\rm{l}}^{3 + }}(aq) + 3{\rm{Zr}}(s)\)

In this reaction, \({\rm{Al}}\) is losing electrons to form \({\rm{A}}{{\rm{l}}^{3 + }}\), so it undergoes oxidation and hence it act as reducing agent.

\({\rm{Z}}{{\rm{r}}^4} + \) is gaining electrons to form \({\rm{Zr}}\), so it undergoes reduction and hence it act as oxidizing agent.

\({\rm{NO}}\)is getting oxidized so, act as reducing agent and \({\rm{Ag}}\) is getting reduced so, act as oxidizing agent.

Consider the following balanced reaction:

\(3A{g^ + }(aq) + NO(g) + 2{{\rm{H}}_2}{\rm{O}}({\rm{l}}) \to 3Ag(s) + {\rm{NO}}_3^ - (aq) + 4{{\rm{H}}^ + }(aq)\)

In this reaction, \({\rm{NO}}\) is losing electrons to form \({\rm{NO}}_2^ - \), so it undergoes oxidation and hence it act as reducing agent.

\({\rm{Ag}} + \) is gaining electrons to form \({\rm{Ag}}\), so it undergoes reduction and hence it act as oxidizing agent.

\({\rm{Mg}}\)is getting oxidized so, act as reducing agent and \({\rm{Si}}{{\rm{O}}_3}^2\) - getting reduced so, it act as oxidizing agent.

Consider the following balanced reaction:

\({\rm{Si}}{{\rm{O}}_3}^{2 - }(aq) + 3{{\rm{H}}_2}{\rm{O}}({\rm{l}}) + 2{\rm{Mg}}(s) \to {\rm{Si}}(s) + 2{\rm{Mg}}{({\rm{OH}})_2}(s) + 2{\rm{O}}{{\rm{H}}^ - }(aq)\)

In this reaction, \({\rm{Mg}}\) is losing electrons to form \({\rm{Mg}}{({\rm{OH}})_2}\), so it undergoes oxidation and hence it act as reducing agent.

\({\rm{SiO}}_3^2\) - is gaining electrons to form \({\rm{Si}}\), so it undergoes reduction and hence it act as oxidizing agent.

\({\rm{Mn}}{{\rm{O}}_2}\)is getting oxidized so, it act as reducing agent and \({\rm{Cl}}{{\rm{O}}_3}\) - getting oxidized so, it act as oxidizing agent.

Consider the following balanced reaction:

\(2{\rm{Mn}}{{\rm{O}}_2}(\;{\rm{s}}) + {\rm{ClO}}_3^ - (aq) + 2{\rm{O}}{{\rm{H}}^ - }({\rm{aq}}) \to 2{\rm{MnO}}_4^ - (aq) + {\rm{C}}{{\rm{l}}^ - }({\rm{aq}}) + {{\rm{H}}_2}{\rm{O}}(l)\)

In this reaction, \({\rm{Mn}}{{\rm{O}}_2}\) is losing electrons to form \({\rm{Mn}}{{\rm{O}}_{{4^ - }}}\), so it undergoes oxidation and hence it acts as reducing agent.

\({\rm{Cl}}{{\rm{O}}_3}\) - is gaining electrons to form \({\rm{C}}{{\rm{l}}^ - }\), so it undergoes reduction and hence it acts as oxidizing agent.