Answer :
(1) 'Na' act as a reducing agent and 'H' act as a oxidizing agent.
(2) 'C' act as a reducing agent and 'O' act as a oxidizing agent.
(3) 'S' act as a reducing agent and 'Mn' act as a oxidizing agent.
Explanation :
Reducing agent : It is defined as the agent which helps the other substance to reduce and itself gets oxidized. Thus, it will undergo oxidation reaction.
Oxidizing agent : It is defined as the agent which helps the other substance to oxidize and itself gets reduced. Thus, it will undergo reduction reaction.
(1) \(2Na+2H_2O(l)\rightarrow 2NaOH(aq)+H_2(g)\)
In this reaction, 'Na' is oxidized from oxidation (0) to (+1) and 'H' is reduced from oxidation state (+1) to (0). Hence, 'Na' act as a reducing agent and 'H' act as a oxidizing agent.
(2) \(C(s)+O_2(g)\rightarrow CO_2(g)\)
In this reaction, 'C' is oxidized from oxidation (0) to (+4) and 'O' is reduced from oxidation state (0) to (-2). Hence, 'C' act as a reducing agent and 'O' act as a oxidizing agent.
(3) \(2MnO_4^-(aq)+SO_2(g)+2H_2O(l)\rightarrow 2Mn^{2+}(aq)+5SO_4^{2-}(aq)+4H^+(aq)\)
In this reaction, 'S' is oxidized from oxidation (-4) to (0) and 'Mn' is reduced from oxidation state (+4) to (+2). Hence, 'S' act as a reducing agent and 'Mn' act as a oxidizing agent.