In the following reaction:
MnO2(s)+4HCl(aq)→MnCl2(aq)+Cl2(g)+2H2O(l)
Identify the oxidising and reducing agents.
MnO2 loses oxygen therefore it is reduced and thus it acts as an oxidizing agent. On the other hand HCl loses hydrogen. It is oxidized thus it acts as a reducing agent.Therefore in the reaction MnO2 is the oxidizing agent and HCl is the reducing agent.