Electrolytic Cells

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Electrolytic Cells

• utilizes electrical energy
• to create chemical energy

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Electrolytic Cells

• electricity used to force non-spontaneous
  reactions to occur endothermic
• electrolytic cells identified by presence of
  battery or power supply

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Electrolytic Decomposition of H2O

• H2 produced at one electrode, O2 at other
• 2H2O energy? 2H2 O2
• Can you tell from the picture which electrode is
  producing H2? Which is producing O2?

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this time Zn is cathode where reduced takes
place Cu is anode where oxidation takes place
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Two kinds of electrolytic cells

• Fused Salt Cells used to purify metals
• (Fused means melted!)
• Electroplating Cells designed to cover a
  surface with metal so will have specific
  properties

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Electroplating
Move desired coating from anode onto object to be
plated Solution contains ions of element to be
plated
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Electroplating Cu onto Al

• Al above Cu in Table J
• reaction will not happen spontaneously so
• use external energy source (power supply or
  battery) to force reaction to occur

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An Ox ate a Red Cat

• anode electrode at which oxidation occurs
• cathode electrode at which reduction occurs
• Electrode polarity opposite than galvanic cell!
• anode is positive
• cathode is negative

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A POX on Electrolytic Cells

• Anode Positive Oxidation
• electrolytic cell polarity determined by outside
  power supply
• anode attached to () terminal
• cathode attached to (-) terminal

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()
Cathode (Obj being Plated)
Reduction Cu2 2e- ? Cu
Note just moving Cu around
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Plating
cathode object to be plated anode - made of
metal want to plate on object solution contains
ions of plating metal
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Fused Salt Cells used to purify metals from
their ores
Ox 2Cl-1 ? Cl2 2e-
Red Na1 1e- ? Na
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• Why does NaCl have to be molten?
• Which electrode will Na1 ions be attracted to?
• Which electrode will Cl-1 ions be attracted to?