Final answer:
In the reaction, chlorine from NaClO2 is oxidized (going from +3 to +4 oxidation state), whereas chlorine from NaOCl is reduced (going from +1 to -1 oxidation state). NaOCl serves as the oxidizing agent, and NaClO2 as the reducing agent.
Step-by-step explanation:
To determine which element is oxidized and which is reduced in the reaction HCl + NaOCl + 2NaClO2 → 2ClO2 + 2NaCl + NaOH, we need to examine the changes in oxidation numbers of the elements involved.
a) The element that is oxidized is chlorine (Cl) in NaClO2 since its oxidation number increases from +3 in NaClO2 to +4 in ClO2.
b) The element that is reduced is also chlorine (Cl), but from NaOCl, where its oxidation number decreases from +1 in NaOCl to -1 in NaCl.
c) The oxidizing agent is NaOCl as it contains the chlorine that gets reduced, while the reducing agent is NaClO2 because it donates the electrons needed for the oxidation of chlorine within its molecule.