1. Electrochemistry

2. Electrochemistry
Electrochemistry is “the study of interchange between chemical change and electrical work”
Redox reactions are reactions involving the transfer of electrons

3. OIL RIG Oxidation: Is Loss of electrons
Reduction: Is Gain of electrons
Oxidation and reduction are the two halves of a redox reaction and the transfer of electrons.

4. Oxidation Numbers: 1, 2, 3…. Pure Element: Oxidation number = 0
Monatomic Ion: Oxidation number = ion’s charge
Ca2+ Oxidation number = +2
Cl Oxidation number = -1
Neutral Compound: Oxidation number = 0
Polyatomic Ion: Oxidation number = sum of all oxidation numbers in ion and/or the ion’s charge
ClO Oxidation number = +1
Oxidation numbers sometimes reffered to as oxidation states

5. Oxidation / Reduction Agents
Reduction Agent --> Oxidized Product
Causes reduction for other product, therefore is the reduction agent.
Oxidising Agent --> Reduced Product
Causes reduction for other product, therefore is the oxidising agent.

6. Balancing a Redox Reaction
Separate and write half-reactions for reduction and oxidation.
Balance elements and electrons (charges) in each half reaction.
Balance number of electrons between half reactions.
Add half reactions and cancel shared components

7. Balancing a Redox Reaction: Part II
Redox with acidic conditions
Balance oxygen using H2O
Balance hydrogen using H+
Redox with basic conditions
Balance oxygen using OH-
Balance hydrogen using H2O
Be sure to check that all charges and atoms that balance

8. Cells (not the ones you’re made of)
Voltaic / galvanic vs. Electrolytic Cells
A galvanic cell is spontaneous
An electrolytic cell is non-spontaneous and requires an outside source of energy
Spontaneous nature of a galvanic cell relates to the energies utilized in oxidation and reduction

9. Cell Components

10. Cathode / Anode and Reduction / Oxidation
Vowels with vowels, and consonants with consonants
ORCA

11. Build a Cell Workshop!

12. E°Cell = cell potential at standard conditions
All elements exist in their standard states
Solutions are 1M
Temperature is 298 K
Pressure at 1 ATM
Degree symbol denotes “standard”

13. Cell Potential cont. E°Cell = E°Cathode - E°Anode
Calculation of standard cell potential using reduction potentials of cathode and anode
E°Cell determines spontaneity of the redox reaction being utilized in the cell
E°Cell > > Spontaneous
E°Cell < > Not Spontaneous
E°Cell = > At Equilibrium

14. Cell Potential and Work
Cell potential can be related to work using the equation for charge
Charge (q) = nF
n = moles of electrons
F = Faraday’s constant
F = 96,485 C / mol e-
C = Coulombs, unit of charge

15. Cell Potential and Work cont.
Given that w = -qE°Cell
The equation w = -nFE°Cell can be derived using the equation for charge
Gibb’s Free Energy (ΔG)
Because ΔG is defined as energy available to do work:
ΔG°= -nFE°Cell
ΔG° determines spontaneity
ΔG° < > Spontaneous
ΔG° > > Not Spontaneous
ΔG° = > At Equilibrium

16. Cell Potential and Equilibrium

17. Nernst Equation

18. Sources
emistry/Balancing_Redox_reactions
Gates’ powerpoint

19. Answers For Handout Oxidation state of sulfur in S2O3 = +3
Oxidation state of oxygen in S2O3 = -2
Oxidation state of calcium in Ca(OH)2 = +2
Oxidation state of nitrogen in N2 = 0
Free Response Answer:
The sign of the cell potential will be positive because (any one is sufficient): K is greater than 1 the reaction is spontaneous (occurs) E° for Sr2+ is more positive Standard reduction potential for Sr more negative E° = V
The oxidizing agent is Mg2+
The cell potential would increase Since all ions are at 1 M, Q for the system is 1 and E° = (RT/nF) ln K so as T increases, so should E°
Ecell will increase In the equation Ecell = E° - ( / n) log Q Q = 0.1 therefore log Q is negative therefore term after E° is positive therefore Ecell increases OR with the concentration of Mg2+ larger than that of Sr2+, Le Chatelier's principle predicts the reaction will have a larger driving force to the right and a more positive Ecell
At equilibrium, Ecell = 0
EoCell = 0.460V
Drawing of the cell requires electrodes (matching the reaction or platinum), porous disk or salt bridge with ions going the correct direction, electron flow the correct direction, salt solution labeled