Topic 13, Redox and Electrochemistry
(Key concepts)

Oxidation-reduction reactions, redox for short, involve the transfer of electrons from one atom to another.  The atom that loses e- is said to be oxidized and the atom that gains electrons is said to be reduced.  You can't have one without the other - oxidation and reduction occur simultaneously.

oil rig:  oxidation is loss, reduction is gain

an ox:  oxidation occurs at the anode

red cat:  reduction occurs at the cathode

electrolytic ant:  the anode is (+) in an electrolytic cell

oxidation half-reactions:

Na  -->  1e-  +  Na+

Zn  -->  2e-  +  Zn+2

reduction half-reactions:

Cl  +  1e-  -->  Cl-

Cu+2  +  2e-  -->  Cu

mass and charge are conserved

the number of electrons lost equals the number of electrons gained

if 2 Cu atoms/ions enter the reaction, 2 Cu atoms/ions come out of the reaction

Voltaic cell:

Electrolytic cell:


Comparing and contrasting voltaic & electrolytic cells:

Similar:  both redox; oxidation occurs at anode in both; reduction occurs at cathode in both; e- flow on wire in both

Different:  voltaic is spontaneous & electrolytic is non spontaneous; voltaic produces electricity & electrolytic uses electricity; voltaic, anode (-) and cathode (+); electrolytic, anode (+) and cathode (-); voltaic has a salt bridge; electrolytic does not; voltaic two containers; electrolytic one container