Question

I just to know how to identify the substance that is reduced, the substance that is oxidized, the oxidizing agent and the reducing agent in each reaction.

As (s) + ClO3-(aq) → H3AsO3 (aq) + HClO(aq)


CN-(aq) + MnO4-(aq) → CNO-(aq) + MnO2(s)

C2H5OH + MnO4- → C2H3O2 - + MnO2

Answer 1

You look to see which elements change oxidation state. The loss of electrons is oxidation. The gain of electrons is reduction.
Here is a site that will show you how to determine the oxidation state of elements in their compounds.
http://www.chemteam.info/Redox/Redox-Rules.html

Here is some info to get you started.
As changes from zero on the left to +5 on the right.
Cl changes from +5 on the left to +1 on the right.
Tip: Don't change H from +1 or O from -2 unless absolutely necessary.