Standard Cell Notation (line notation)
• Conventions:
 Anode on Left
 Single line : represent phase boundaries
 Two line : represent liquid junction
e-
V
e-
Zn
Zn2+
Cu
Cu2+
NO3-
NO3
-
Anode / anode solution // cathode solution / Cathode
Example:
Zn / Zn2+ (1.0 M) // Cu2+ (1.0M)
/
Cu
Line Notation
•
solidAqueousAqueoussolid
•
•
•
•
Anode on the leftCathode on the right
Single line different phases.
Double line porous disk or salt bridge.
If all the substances on one side are
aqueous, a platinum electrode is indicated.
For the last reaction
Cu(s)Cu+2(aq)Fe+2(aq),Fe+3(aq)Pt(s)
Cu2+
Fe+2
17_360
e–
e–
e–
e–
Porous disk
Oxidation
e–
(a)
Reducing
agent
Anode
Reduction
Oxidizing
agent
(b)
e–
Cathode
Copyright McGraw-Hill 2009
7
Practice:
In a galvanic cell, the electrode that acts as a
source of electrons to the solution is called
the __________; the chemical change that
occurs at this electrode is called________.
a. cathode, oxidation
b. anode, reduction
c. anode, oxidation
d. cathode, reduction
Practice
Under standard conditions, which of the
following is the net reaction that occurs in
the cell?
Cd|Cd2+ || Cu2+|Cu
a. Cu2+ + Cd → Cu + Cd2+
b. Cu + Cd → Cu2+ + Cd2+
c. Cu2+ + Cd2+ → Cu + Cd
d. Cu + Cd 2+ → Cd + Cu2+
Galvanic Cell
•
•
1.
2.
3.
4.
The reaction always runs spontaneously in the
direction that produced a positive cell potential.
Four things for a complete description.
Cell Potential
Direction of flow
Designation of anode and cathode
Nature of all the components- electrodes and
ions
Oxidation Numbers on the Periodic Table
Cell Potential
• Cell Potential / Electromotive Force
(EMF):
•
The “pull” or driving force on electrons
•
Measured voltage (potential difference)
• The total cell potential is the sum of the
potential at each electrode.
17_363
e–
e–
Zn(s)
e–
Ecell = +1.10 V
+
Zn 2
–
SO 4 2
1.0 M Zn 2
solution
Anode
e–
+
Cu 2
–
SO 4 2
+
+
1.0 M Cu 2
solution
Cathode
Cu(s)
Cell Potential,
E0cell
0
E
cell
cell potential under standard conditions
elements in standard states (298 K)
solutions:
1M
gases:
1 atm
Practice
• Completely describe the galvanic cell based on the
following half-reactions under standard conditions.
• MnO4- + 8 H+ +5e-  Mn+2 + 4H2O
Eº=1.51 V
• Fe+3 +3e-  Fe(s)
Eº=0.036V