1. Know the rules for assigning oxidation numbers. Be careful of the exceptions.
2. Free elements always have an oxidation # of 0. It’s the easiest way to recognize a redox rxn.
3. Redox rxns involve a change in oxidation numbers.
4. LEO and GER
5. When electrons are lost they appear on the product side of an equation.
6. When electrons are gained they appear on the reactant side of an equation.
7. Always balance for mass and charge. Electrons gained = electrons lost.
8. Oxidizing agents are the species reduced
9. Reducing agents are the species oxidized.
10. Know the difference between an atom and an ion.
11. Metal atoms can never be reduced. Only metal ions are reduced.
12. Know how to read Table J backwards and forwards.
13. The more reactive metal is always oxidized.
14. Electrochemical (i.e. volataic) cells produce an electric current through a spontaneous redox rxn
15. Electrolytic cells use a power source to force a non spontaneous redox rxn
16. Anox- more active metal always the anode, site of oxidation
17. Redcat- less active metal is cathode site of reduction, but the less reactive metal ion is the species reduced.
18. Electrons flow anode to cathode through the wire
19. Salt bridge allows for ION migration
20. At equilibrium the voltage = zero (the battery is dead)
21. Know the differences between voltaic and electrolytic cells.
Zn + Cu2+ à Zn2+ + Cu
The zinc is oxidized an acts as the reducing agent. This takes place at the anode.
The Cu2+ is reduced and acts as the oxidizing agent. This takes place at the cathode.
The correct half reactions:
Oxidation: Zn à Zn2+ + 2 e
Reduction: Cu2+ + 2 e à Cu