Electrode potentials
To compare electrode potentials of different species:measured against a common
reference or standard
● Ion concentration of 1.00 mol dm-3
● A temperature of 298 K
● A pressure of 100 kPa
- high resistance voltmeter: no current flows
Electrode potentials measured relative to a standard hydrogen electrode with 0.00V
Standard electrode potential (Eθ) is the potential difference (or voltage) produced when
a standard half-cell is connected to a standard hydrogen cell under standard conditions
The standard hydrogen electrode is a half-cell used as a reference electrode and
consists of hydrogen gas in equilibrium with H + ions of concentration 1.00 mol dm-3
● Reduction occurs at the positive electrode
● Oxidation occurs at the negative electrode
● Inert platinum wire or foil is used as an electrode to make electrical contact with
the solution
ELECTROCHEMICAL CELLS
○ Phase boundary (interface between a solid and a solution)
○ Salt bridge with mobile ions that complete circuit (KCl/KNO3- as soluble =
no precipitates affecting equilibrium position)
○ Highest oxidation state drawn next to salt bridge
○ Cell potential difference is shown with the polarity of the right hand
electrode
E.g. Zn (s)∣Zn2+ (aq) ∥Cu2+ (aq)∣Cu (s) E cell = +1.10 V
Copper half cell is more positive than zinc half cell: electrons flow from zinc to copper
To compare electrode potentials of different species:measured against a common
reference or standard
● Ion concentration of 1.00 mol dm-3
● A temperature of 298 K
● A pressure of 100 kPa
- high resistance voltmeter: no current flows
Electrode potentials measured relative to a standard hydrogen electrode with 0.00V
Standard electrode potential (Eθ) is the potential difference (or voltage) produced when
a standard half-cell is connected to a standard hydrogen cell under standard conditions
The standard hydrogen electrode is a half-cell used as a reference electrode and
consists of hydrogen gas in equilibrium with H + ions of concentration 1.00 mol dm-3
● Reduction occurs at the positive electrode
● Oxidation occurs at the negative electrode
● Inert platinum wire or foil is used as an electrode to make electrical contact with
the solution
ELECTROCHEMICAL CELLS
○ Phase boundary (interface between a solid and a solution)
○ Salt bridge with mobile ions that complete circuit (KCl/KNO3- as soluble =
no precipitates affecting equilibrium position)
○ Highest oxidation state drawn next to salt bridge
○ Cell potential difference is shown with the polarity of the right hand
electrode
E.g. Zn (s)∣Zn2+ (aq) ∥Cu2+ (aq)∣Cu (s) E cell = +1.10 V
Copper half cell is more positive than zinc half cell: electrons flow from zinc to copper
