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Cells
Electrochemical Cells
• Use Redox reactions
• Involves transfer of electrons
• 2 types
– Voltaic
– Electrolytic
Voltaic Cells
• Spontaneous reaction
• Converts chemical energy to electrical
energy
• Composed of two separate “half cells”
– Contain electrolyte (salt) solutions
• Cells are connected in a circuit
• Contain two electrodes
AN OX and a REDCAT
• 2 Different electrodes
Anode (-)
– Site of oxidation (An Ox)
– Lose electrons and
produce positive ions
– Ions fall off the metal
electrode into solution
– Mass of electrode
decreases
– *Remember VAN= Voltaic
Anode Negative
Cathode (+)
– Site of Reduction
– Ions in solutions are
attracted to electrons lost
by Anode
– Ions are reduced to form
Atoms
– Atoms attach to metal
electrode
– Mass of metal increases
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Voltaic Cells
• Wire- electrical conductor in which electrons are
transferred
– Connects two electrodes
– Electrons flow from Anode to cathode
• Salt Bridge- connects the 2 solutions and allows
ions to be transferred
– maintains neutrality and completes electrical circuit
– electrical current can be produced
Electrodes
• How do you know which metal makes
which electrode?
– Table J
• Higher metal on the table (Oxidized)
– Anode
• Lower metal on the table (Reduced)
– Cathode
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Electrolytic Cells
• Pb +Zn(NO3)2
Electrolytic Cells
Zn + Pb(NO3)2
• Yes this reaction can occur
• Not Spontaneous
– Electroplating
• Use electricity to force electrons to flow in
opposite directions
Electrolytic Cells
• Force silver (or other metals) to be oxidized
(shrink in size)
Similarities Between two cells
• Both use redox
– This is the anode (+ terminal)
• The spoon (or object) is electroplated or reduced
(coated in metal)
• REDuction at cathode
– This the cathode (- terminal)
• Battery (or electrical supply) forces electrons to
flow
• Spoon (or object) winds up coated in silver (or
another metal)
• Anode oxidation
• Electrons flow from anode to cathode
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Differences
• Voltaic is spontaneous, electrolytic uses
electricity to force reaction to occur
• http://www.kentchemistry.com/links/Redox
/flash/halfcells.swf
• Voltaic- anode is negative, cathode
positive
• Electrolytic- Anode is positive, cathode is
negative
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