Question #cdd5a

1 Answer
Nov 6, 2015

In the first reaction, the oxidation state of Cl in HCL is -1 and it changes to 0 in the free form of #Cl_2#. Hence it lost electrons and so was reduced.
Similarly the oxidation state of Mn in #MnO_2# is 4+ and this becomes 2+ in #MnCl_2# so the Mn gained electrons and was reduced.
By definition, HCL is then the oxidizing agent and #MnO_2# is the reducing agent.

A similar analysis may be applied in the second reaction to show that since #Zn -> Zn^(2+) and H^+->H_2#, it means that Zn was oxidized since it lost electrons, and H was reduced since it gained electrons. (Cl is a spectator ion here as its oxidation state does not change).
So then by definition, Zn is the reducing agent and HCL is the oxidizing agent.