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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