KOH

Pb-Acid H
2
SO
4

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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.
1.
Spontaneous redox reaction
2.
Produces electricity from chemicals
3.
Is commonly called a battery
The salt bridge allows ions to migrate from one half-cell to the other without allowing the solutions to mix.

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 .

For any cell
Oxidation always occurs at the anode and reduction at the cathode
Electrons flow through the wire and go from anode to cathode
Anions (- ions) migrate to the anode and cations (+ions) migrate towards the cathode usually through the salt bridge

1. Draw and completely analyze a Cu/Sn electrochemical cell.
Higher
Greatest Electron Affinity
Reduction
Cathode
Cu 2+ + 2e → Cu
(s)
0.34 v
Gains mass e
Cu
-
+
Cu 2+
NO
3
voltmeter
0.48 v
Na -+
NO
3
-
Overall Reaction: Cu 2+ + Sn → Sn 2+ + Cu
(s)
Sn 2+
NO
3
-
0.48 v e -
Sn
Lower
Oxidation
Anode
Sn
(s)
→ Sn 2+ + 2e -
+0.14 v
-
Loses mass

The Hydrogen half cell involves a gas and requires an inert or nonreactive Pt electrode.
Wire to circuit
H
2(g) in
H +
Cl -
Pt
(s)
1 M HCl

Draw a H
2
/Ag electrochemical cell with a KNO
3 salt bridge.
2e voltmeter
0.80 v
1.0 M KNO
3
2e -
oxidation
Anode
H
H
2
→ 2H
0.00 v
+ + 2e pH decreases
Pt
2
H +
Cl -
NO
3
K +
Ag +
NO
3
-
Ag
Higher
Greater electron affinity
Reduction
Cathode
+
Ag + + 1e → Ag
(s)
+0.80 v
Gains mass
1 M HCl 1 M AgNO
3
2Ag + + H
2
→ 2Ag + 2H + 0.80 v