Cells

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Cells

• Electrochemical
• Electrolytic

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Examples of electrolytic cells Requires a power
source to force a non-spontaneous redox reaction
to occur

• Electroplating a metal
• Electrolysis of water
• Recharging a rechargeable battery

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Electroplating

• Must contain an object to be plated (cathode
  cite of reduction metal ion becoming metal
  atoms), the plating metal (anode cite of
  oxidation metal atoms becoming metal ions) and a
  solution containing cations of the plating metal.

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Below is an example of electroplating an object
with silver
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Electrolysis of water using electricity to
split water into elements
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Explanation of the electrolysis of water

• The anode (oxidation reaction)
• O-2 ? O2(g) 2e-
• The cathode reaction (reduction reaction)
• 2H 2e- ? H2(g)

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Examples of Electrochemical Cells Spontaneous
redox reactions producing electrical current.

• Voltaic Cells (Daniell Cell)
• Dry Cell Battery
• Wet cell Battery (such as the lead storage
  battery)

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Voltaic Cells
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Dry Cells
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Details of Dry Cell Battery

• The anode reaction is
• Zn ? Zn2 2e-
• The Cathode reaction is
• 2NH4(aq) 2e- -gt 2NH3(g) H2(g)

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Problems??

• Note at the cathode reaction, the production of
  two gases! Why dont dry cell batteries
  explode??
• See the next slide for answers!!

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Why dont Dry Cell Batteries explode?

• ZnCl2(aq) 2NH3(g) -gt Zn(NH3)2Cl2(s)
• 2MnO2(s) H2(g) -gt Mn2O3(s) H2O(l)
• Resulting in the following net cathode reaction
• 2NH4(aq) 2MnO2(s) 2e- -gt Mn2O3(s) H2O(l)
  2NH3(aq)

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Lead Storage Battery (Car Battery)
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How are car batteries used and charged? below
is when it is used
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How are car batteries used and charged? below
is when it is recharged
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Fuel Cells

• There are many types of fuel cells the most
  widely discussed are the PEM fuel cells because
  of their potential application to the auto
  industry.
• Click here to see how these work.

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Efficiency 70Operating Temperature (150 200
oC)Output up to 5 kWatts
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Efficiency 60 80Operating Temperatures
650 oCOutput up to 100 Mwatts
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Efficiency 40 80 Operating Temperature
150 200 oCOutput up to 200 kWatts