Electrochemical cells
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Transcript of Electrochemical cells
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Presentation by-Saurav K Rawat (CHEMSO President)
Chemical Society, St John’s College AgraELECTRO-CHEMISTRY
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Electrochemistry
Electrochemical Cells
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Electrochemical cells are Batteries
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Alkaline Batteries
KOH
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Car Batteries
Pb-Acid H2SO4
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Mitsubishi iMiEV - Pure Electric Car
Powered by a 330 v Li-Ion Rechargeable battery
Plugs into your house and takes 14 hours to charge -100 km for $ 0.60
$ 50,000 Can
$ 36,000 US
Top Speed 130 km/h 63 hp and 133 lb.-ft. of torque
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Cell Phone batteries
Lithium Ion Rechargeable battery
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Lithium Coin Cell
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Space Ship Batteries
Powered by Radioisotopes
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Ni-Metal Hydride
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Notes on Electrochemical Cells
An electrochemical cell – a system of electrodes, electrolytes, and salt bridge that allow oxidation and reduction reactions to occur and electrons to flow through an external circuit.
The salt bridge allows ions to migrate from one half-cell to the other without allowing the solutions to mix.
1. Spontaneous redox reaction 2. Produces electricity from chemicals
3. Is commonly called a battery
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Analyzing Electrochemical Cells
The reaction that is higher on the reduction chart is the reduction and the lower is oxidation and is written in reverse.
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For any cell Oxidation always occurs at the anode and reduction at the cathodeElectrons flow through the wire and go from anode to cathodeAnions (- ions) migrate to the anode and cations (+ions) migrate towards the cathode usually through the salt bridge
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voltmeter
1. Draw and completely analyze a Cu/Sn electrochemical cell.
Higher
Greatest Electron Affinity
Reduction
Cathode
Cu2+ + 2e- → Cu(s)
0.34 v
Gains mass
+
CuSn
Cu2+
NO3-
Sn2+
NO3-Na-+
NO3-
0.48 v
Lower
Oxidation
Anode
Sn(s) → Sn2+ + 2e-
+0.14 v
Loses mass
-
Overall Reaction: Cu2+ + Sn → Sn2+ + Cu(s) 0.48 v
e-e-
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The Hydrogen half cell involves a gas and requires an inert or nonreactive Pt electrode.
H2(g) in
Wire to circuit
Pt(s)
1 M HCl
H+
Cl-
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1.0 M KNO3
0.80 v 0.80 v
AgH2
voltmeter 2e-
2e-
H+
Cl-
Ag+
NO3-
NO3
- K+
2Ag+ + H2 → 2Ag + 2H+ 0.80 v
Draw a H2/Ag electrochemical cell with a KNO3 salt bridge.
HigherGreater electron affinityReductionCathode+
Ag+ + 1e- → Ag(s)
+0.80 vGains mass
oxidationAnode-
H2 → 2H+ + 2e-
0.00 vpH decreases
1 M HCl 1 M AgNO3
Pt
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