STANDARD ELECTRODE POTENTIALS

 

See Chemical Ideas 9.2 Redox reactions and electrode potentials for details

The value of E indicates the willingness of a half-cell to be reduced (i.e. it is a reduction potential).

It shows the how many volts are required to make the system undergo the specified reduction, compared to a standard hydrogen half-cell, whose standard electrode potential is defined as 0.00 V.  At the top of the list is the most powerful reducing agent – the species that is least easily reduced.

Standard conditions are 298 K temperature, 1 atm pressure and 1.0 mol dm-3 concentrations.

 

Ecell = E(right-hand electrode) – E(left-hand electrode)

(all under standard conditions)

 

HALF CELL

NOTES

REDUCTION HALF-EQUATION

E / Volts (standard conditions)

 

Lithium

 

Li+(aq) + e- Li(s)

-3.04

Potassium

 

K+(aq) + e- K(s)

-2.92

Barium

 

Ba2+ (aq) + 2e- Ba(s)

-2.90

Calcium

 

Ca2+ (aq) + 2e- Ca(s)

-2.84

Sodium

 

Na+(aq) + e- Na(s)

-2.71

Magnesium

 

Mg2+(aq) + 2e- Mg(s)

-2.37

Aluminium

 

Al3+(aq) + 3e- Al(s)

-1.68

Manganese(II)

 

Mn2+ (aq) + 2e- Mn(s)

-1.18

Zinc

 

Zn2+(aq) + 2e- Zn(s)

-0.76

Chromium(III)

 

Cr3+ (aq) + 3e- Cr(s)

-0.74

Iron(II)

 

Fe2+(aq) + 2e- Fe(s)

-0.44

Chromium(III)-(II)

 

Cr3+ (aq) + e- Cr2+ (aq)

-0.41

Cadmium

 

Cd2+(aq) + 2e- Cd(s)

-0.40

Cobalt(II)

 

Co2+(aq) + 2e- Co(s)

-0.28

Nickel(II)

 

Ni2+(aq) + 2e- Ni(s)

-0.26

Tin(II)

 

Sn2+(aq) + 2e- Sn(s)

-0.14

Lead(II)

 

Pb2+(aq) + 2e- Pb(s)

-0.13

 

Hydrogen

Special conditions.  See Chemical Ideas page 213 figure 11.

2H+(aq) + 2e- H2(g)

+0.00

 

Tin(IV)

 

Sn4+(aq) + 2e- Sn2+(aq)

+0.15

Copper(II)-(I)

 

Cu2+(aq) + e- Cu+(aq)

+0.15

Copper(II)

 

Cu2+(aq) + 2e- Cu(s)

+0.34

Oxygen-water

 

O2(g) + 2H2O (l) + 4e- 4OH-(aq)

+0.40

Copper(I)

 

Cu+(aq) + e- Cu(s)

+0.52

Iodine

Inert platinum electrode, aqueous solution of iodide ions and iodine molecules.

I2(aq) + 2e- 2I-(aq)

+0.54

Manganese(VII)-(IV)

 

Mn7+(aq) + 3e- Mn4+(aq)

+0.58

Iron(III)-(II)

 

Fe3+(aq) + e- Fe2+(aq)

+0.77

Mercury(I)

 

Hg22+ + 2e- 2Hg(s)

+0.79

Silver

 

Ag+(aq) + e- Ag(s)

+0.80

Bromine

Inert platinum electrode, aqueous solution of bromide ions and bromine molecules.

Br2(aq) + 2e- 2Br-(aq)

+1.07

Manganese(IV)-(II)

 

Mn4+(aq) + 2e- Mn2+(aq)

+1.21

Oxygen-acid

Oxygen gas dissolved in an acidic aqueous solution

O2(g) + 4H+(aq) + 4e- 2H2O(l)

+1.23

Hydrogen peroxide

 

H2O2(aq) + 2H+(aq) + 2e- 2H2O(l)

+1.23?

Dichromate(VII)

Acidified dichromate(VII) solution

Cr2O72-(aq) + 14H+(aq) + 6e- 2Cr3+(aq) + 7H2O(l)

+1.36

Chlorine

Inert platinum electrode, aqueous solution of chloride ions and chlorine molecules.

Cl2(aq) + 2e- 2Cl-(aq)

+1.36

Gold(III)

 

Au3+(aq) + 3e- Au(s)

+1.50

Manganate(VII)

Acidified manganate(VII) solution

MnO4-(aq) + 8H+(aq) + 5e- Mn2+(aq) + 4H2O(l)

+1.51

Cobalt(III)-(II)

 

Co+3(aq) + e- Co2+(aq)

+1.82

Fluorine

 

F2(aq) + 2e- 2F-(aq)

+2.87

 

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