6050030
Description
Mind Map by Eilidh Young, updated more than 1 year ago
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Created by Eilidh Young
over 9 years ago
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Standard Electrode Potentials
- Under standard conditions (pressure of
hydrogen gas 1 atm, acid concentration of 1 mol
L-1), the potential for the reduction reaction
below is assigned a value of zero vaults
- 2H+(aq) + 2e- <--> H2(g) Eo = 0.00V
- 2H+(aq) + 2e- <--> H2(g) Eo = 0.00V
- For any redox couple, the standard electrode
(reduction) potential is the voltage obtained
under standard conditions when that half-cell is
connected to the standard hydrogen electrode
- Experimentally, the more positive terminal is always
where reduction is occurring in a spontaneous reaction
- Experimentally, the more positive terminal is always
where reduction is occurring in a spontaneous reaction
- Example
- The cell potential for the electrochemical cell below is +0.76V:
Zn(s) | Zn2+(aq) || H+(aq) | H2(g) | Pt(s)
- The Zn electrode is the negative and
the standard reduction potential for
the Zn2+/Zn half cell is -0.76V
- If the Zn2+/Zn electrode is replaced
with a Cu2+/Cu electrode, the Cu2+ is
reduced and the H2 gas is oxidised
- The Cu electrode is positive and
the Cu2+ | Cu couple will have a
positive reduction potential
- The voltmeter has a reading of +0.34V:
Pt(s) | H+(aq) | H2(g) || Cu2+(aq) | Cu(s)
- The voltmeter has a reading of +0.34V:
Pt(s) | H+(aq) | H2(g) || Cu2+(aq) | Cu(s)
- The Cu electrode is positive and
the Cu2+ | Cu couple will have a
positive reduction potential
- If the Zn2+/Zn electrode is replaced
with a Cu2+/Cu electrode, the Cu2+ is
reduced and the H2 gas is oxidised
- The Zn electrode is the negative and
the standard reduction potential for
the Zn2+/Zn half cell is -0.76V
- When comparing standard reduction potentials, the species
on the left in the couple with the most positive reduction
potential will be the strongest oxidising agent or oxidant
- As the electrode potential
decreases, the strength of
oxidant species decreases,
while strength of reductant
species increases
- As the electrode potential
decreases, the strength of
oxidant species decreases,
while strength of reductant
species increases
- The cell potential for the electrochemical cell below is +0.76V:
Zn(s) | Zn2+(aq) || H+(aq) | H2(g) | Pt(s)
- When comparing standard reduction
potentials, the species on the left in the couple
with the most positive reduction potential will
be the strongest oxidising agent or oxidant
- As the electrode potential decreases, the
strength of the oxidant species decreases,
while strength of reductant species increases
- As the electrode potential decreases, the
strength of the oxidant species decreases,
while strength of reductant species increases
- Using reduction potentials
to determine Eo cell
- In any electrochemical cell, Eo
cell = Eo (reduction half-cell) -
Eo (ocidation half-cell) or Eo
cell = Eo (cathode) - Eo (anode)
- The couple with the more positive
reduction potential will be the
reduction half-cell (cathode)
- The couple with the more positive
reduction potential will be the
reduction half-cell (cathode)
- A more reactive metal will reduce
the cation of a less reactive metal,
as the Eo cell value for the reaction
will be positive (the more reactive
metal is the reductant in the redox
couple with the lower Eo value
- Despite a positive standard
cell potential, a reaction
may be very slow due to a
high activation energy
- A reaction may not
proceed if the surface
of the metal is
coated with an oxide
- A reaction may not
proceed if the surface
of the metal is
coated with an oxide
- In any electrochemical cell, Eo
cell = Eo (reduction half-cell) -
Eo (ocidation half-cell) or Eo
cell = Eo (cathode) - Eo (anode)
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