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Lecture

Cell potential, spontaneity, half-cell potentials

2 pages32 viewsSpring 2011

Department
Chemistry
Course Code
CHEM 113
Professor
Lisa Dysleski

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2 May
Final Exam
May 10th
2 – 4
Clark A203
Voltaic (galvanic cell) – uses a spontaneous reaction to produce electrical energy (ΔG < 0)
Electrolytic cell – uses electrical energy to drive a non-spontaneous reaction (ΔG > 0)
Cell – half-reactions are separated
Oxidation node – anode
Reduction node – cathode
Need salt bridge to complete circuit
Why are some electrochemical processes spontaneous and others are not?
In a voltaic cell, the free energy change of a spontaneous reaction is converted into the
kinetic energy of electrons moving through the cell
Ecell = cell potential (also voltage)
A cell potential is made up of two half cell potentials
Zn (s) → Zn2+ (aq) + 2e-zinc = 0.76 V
Cu 2+
(aq) + 2e -
→ Cu (s) copper = 0.34 V
Zn (s) + Cu2+ (aq) → Cu (s) + Zn2+ (aq) cell = 1.10 V
Cells end when it goes to equilibrium
Each half-cell potential is measured against a standard electrode
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