General Bonding considerations

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General Bonding considerations
Write an essay on Electrode Potentials.
AL Chemistry
# Guidelines #
0. Introduction: Importance of Electrode Potentials
in Electrochemistry
& Redox Reactions
p. 1
# Guidelines (con’t) #
AL Chemistry
1. What are Electrode Potentials?
(a) Reactivity and Potential Difference
in M / Mn+ system: reactivity of metal 
tendency to give out e- 
Mn+ + n e-
M
(redox eqm!)
greater extent of charge separation
greater “potential difference”
p. 2
# Guidelines (con’t) #
AL Chemistry
potential difference (p.d.):
 absolute p.d. cannot be measured!
 instead, measure the “relative value”
with respect to a “reference electrode”.
“standard hydrogen electrode”
“electrode potential”
p. 3
# Guidelines (con’t) #
AL Chemistry
2. How are Electrode Potentials measured?
(a) Measured under Standard Conditions
 eqm position affected by:
(i) concentration
(ii) temperature
(iii)pressure
 define standard conditions as 1M, 298K, 1 atm
 “standard electrode potential”
p. 4
# Guidelines (con’t) #
AL Chemistry
(b) Connecting with SHE with Salt Bridge
 compare the tendency to give out ewith SHE
 if > SHE,  -ve. E value [strong R.A.]
 if < SHE,  +ve. E value [strong O.A.]
 measured E value by a potentiometer
= emf = max. p.d. between two half cells
p. 5
# Guidelines (con’t) #
AL Chemistry
3. How are Electrode Potentials used?
(a) Calculation of cell emf
Ecell = E2 – E1
E1 < 0
E2 > 0
half cell X
half cell Y
[anode]
E H+|H2 = 0V
[SHE]
[cathode]
p. 6
# Guidelines (con’t) #
AL Chemistry
(b) Predict Energetic Feasibility of
Redox Reactions
 E value > 0 ----- energetically feasible
 no information on the Activation Energy
 reactions may be very slow!
p. 7

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