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