Modern inorganic chemistry

98 ACIDS AND BASES. OXIDATION AND REDUCTION

^=—H 5

Figure 4.4. The hydrogen electrode

Standard redox potentials for metals (usually called electrode
potentials), E"^9 ", are measured at 298 K relative to a standard
hydrogen electrode for the pure metal in a solution containing
Imoir^1 of its ions and at pH = 0 (i.e. containing ImolT^1
hydrogen ions). (The importance of pH is stressed later, p. 101.) If
the metal is a better reducing agent than hydrogen the metal will

Table 4.2

STANDARD REDOX POTENTIALS OF SOME COMMON METALS

Reaction E~~(V\

Li + (aq) + e ~» Li(s)

K+(aq) + e~ -»K(s)

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

Ca^2 + (aq) + 2e~~ -» Ca(s)

> Na(s)

Mg2+(aq) 2e~

Al^3 + (aq) + 3e

Zn^2 + (aq) + 2e

Fe2+(aq) + 2e

Pb^2 + (aq) + 2e

Cu*' + (aq) + 2e

Ag + (aq) + e~

Au^3 *(aq) -I- 3f

* Mg(s)

* Al(s)

-* Zn(s)

* Fe(s)

* Ni(s)

* Sn(s)

H. Pb(s)

» Fe(s)

-»• Cu(s)

* Ag(s)

• Hg(s)
  -* Au(s)

H 2 0(l)

Increasing

reducing

power

-2.87

-2.71

-2.37

-1.66

-0.76

-0.44

-0.25

-0.14

-0.13

-0.04

0.00

+ 0.34

+ 0.80

+ 0.86

+ 1.50