Standard Cell Notation (line notation)
• Conventions:Anode on LeftSingle line : represent phase boundariesTwo line : represent liquid junction
Cu2+
V
NO3-
Zn2+
NO3-
CuZn
e-
e-
Anode / anode solution // cathode solution / Cathode
Example: Zn / Zn2+ (1.0 M) // Cu2+ (1.0M) / Cu
Line Notation
• solid½Aqueous½½Aqueous½solid
• Anode on the left½½Cathode 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 reactionCu(s)½Cu+2(aq)½½Fe+2(aq),Fe+3(aq)½Pt(s)
Cu2+ Fe+2
17_360
Porous disk
Reducingagent
Oxidizingagent
e –
e –
e – e –
e –
e –
CathodeAnode (b)(a)
Oxidation Reduction
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
• The reaction always runs spontaneously in the direction that produced a positive cell potential.
• Four things for a complete description.
1. Cell Potential
2. Direction of flow
3. Designation of anode and cathode
4. 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 – e–
e–
Zn 2+
SO4 2–
Zn(s)
1.0 M Zn 2+
solution
Anode
1.0 M Cu 2+
solution
Cathode
Cu 2+
SO4 2–
Cu(s)
Ecell = +1.10 V
Cell Potential, E0cell
E0cell
cell potential under standard conditions
elements in standard states (298 K)
solutions: 1 M
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