Core Reactions: Redox
Slide 26 of 42
Redox Reaction Type 3: Complex Redox Reactions
Note that oxidizing agents have more oxygen than reducing agents or have bigger positive charge.
–Those with oxygen are able to liberate oxygen which removes or accepts electrons from the reducing agents.
Combining an oxidizing agent and a reducing agent under appropriate conditions will result in a redox reaction.
–2MnO4- (aq) + 6H+ (aq) + 5NO2- ® 2Mn2+ (aq) + 5NO3- (aq)+ 3H2O(aq)
–Pink         Colorless
–MnO4 + 8H+ + 5Fe2+    Mn2+ + 5Fe3+ + 4H2O
–Cr2O72- (aq) + 3SO32-(aq) + 8H+ (aq) ® 2Cr3+ (aq) + 3 SO42- (aq) + 4H2O (l)
–Orange              Green
These redox reactions are a lot more complex because they involve three reagents; the third reagent being an acid (H+).
–In other words, these redox reactions require an acidic medium to occur.
–As a matter of fact, they are so complex that they require a completely different methos of balancing them! (See Core Reactions - Balancing Redox rxn in acid.)