Standard Electrode Potential
Standard
Electrode Potential
The hydrogen electrode can now be
combined with any suitable half-cell (metal or gas) electrode and the potential
difference between the two half-cells determined. If a standard hydrogen electrode
is combined with a metal electrode dipping in 1M metal ions at 25°C, the
measured potential difference is the standard electrode potential of the metal
since by definition E°H/H+ =0 V.
A galvanic cell consisting of the
hydrogen electrode and the copper half-cell is written as:
Pt, H2(g)
(1 atm)/H+(aq) 1MJ//Cu2+ (1 M)/Cu(S)
The single vertical line represents the
separation of phases (e.g. solution and solid) and the double vertical lines
represent the salt-bridge.
The standard procedure of writing the
electrochemical cell is to place the hydrogen electrode on the left-hand side
and the other electrode on the right-hand side. The measured potential
difference of such a cell under standard conditions is called the standard
electrode potential or the standard reduction potential of the electrode under
study and is given the symbol E°. If the left electrode is another one other
than the hydrogen electrode, then the measured potential difference is the
standard potential of the cell.
The measured potential difference (or
cell electromotive force, e.m.f) of the above cell under standard conditions is
0.34V. This is the standard e.m.f of the cell and also the standard electrode
potential of the copper half-cell (or copper electrode).
Comments
Post a Comment