Redox and Electrochemistry Flashcards
REDOX reactions abbreviation
LEORA
GEROA
in Oxidation reactions, where are the electrons?
in Reduction, where?
OHR: e- is in products side
RHR: e- is in reactants side
9 general rules for oxidation number
- 0 charge for elements
- ion charge for monoatomic ion
- in a molecule, sum of O.N. values is 0
- in polyatomic ion, sum of O.N. values is ion charge
- Group 1 = +1
- Group 2 = +2
- Group 17 = -1 w metals
- Hydrogen
+ 1 w nonmetals
-1 w metals - Oxygen
-2 most of the time
-1 in peroxides
-1/2 in superoxide
Reducing Agent vs Oxidizing Agent
RA undergoes oxidation reaction
OA undergoes reduction reaction
Clues to use in identifying the ff:
- peroxides
- superoxides
PEROXIDES
- O2 with another element except GROUP 1
- O2 with GROUP 1 subscript 2 (Li2O2 ; H2O2 ; Na2O2)
SUPEROXIDES
- O2 with GROUP 1 (NaO2 ; RbO2 ; KO2)
Are coefficients included when agents are assigned?
No… only the main molecule/element
What are 3 rules when balancing chemical reactions using CON method
- Bawal galawin si OA and RA after balancing the reactants side
- Adjust the rest of the reactions accordingly
- Check if coefficients are simplifiable
2 types of redox reactions
- Disproportional
- Comproportional
TYPES OF REDOX REACTIONS
a species (only 1) is simultaneously reduced and oxidized
Disproportional
TYPES OF REDOX REACTIONS
2 reactants (w same element but diff ON) form a product with its ON a value between the reactants
Comproportional
2 TYPES OF ELECTROCHEMICAL CELLS
- produces… through…
- spontaneous or non spontaneous
- energy requiring or not
- system or surroundings does work?
VOLTAIC (Galvanic Cell)
- produces electricity through chemical reaction
- spontaneous
- does not need energy
- system does work on surroundings
Electrolytic Cell
- produces chemical reaction through electricity
- non - spontaneous
- needs energy
- surroundings does work on system
7 components of a voltaic cell
Anode (s)| Reducing Agent (aq) || Oxidizing Agent (aq) | Cathode (s)
|| - Salt bridge (neutralizes the 2 solutions)
… | …. Phase boundaries
, - Same phases
- Phase boundaries
Anode vs Cathode
Anode - gives e-
Cathode - receives e-
How to create the Net Cell Reaction from OHR and RHR
Cancel the e- and combine reactants & products
Standard value for voltmeter
1.10 V
In the STANDARD REDUCTION POTENTIAL TABLE, what does a more positive E° value signify?
Higher tendency to be reduced (gain e-)
In voltaic cell, how to identify which is the RHR and OHR?
RHR: more positive E° value
OHR: less positive E° value
Basis reaction of the standard reduction potential table
2H3O+ + 2e- -> H2 + 2H2O
at 0.00 V
3 conditions of the STANDARD REDUCTION POTENTIAL TABLE
- all ionic species at 1 M
- all gases at 1 atm
- 25 °C
What do you call the mock-up voltaic cell with Zn as ANODE and Cu as CATHODE?
The Daniell Cell
If either cathode or anode does not have a solid metal, what is used as replacement?
An inert metal
Pt
What do you call the difference between the potential of anode and cathode? (2)
Cell potential / Cell voltage
Formula for cell potential (2)
E° cell = E° cathode - E° anode
E° cell = E° red + E° ox
2 conventions of cell potential
- reaction multiplied by a factor = remain unchanged
- reverse reaction = opposite sign only
is E° an extensive or intensive property
intensive
What do you call the mock-up electrolytic cell with Na as CATHODE and Cl as ANODE
Downs Cell
What does the DOWNS CELL produce (2)
Na metal
Cl2 gas
In electrolytic, how do you identify the RHR and OHR?
RHR: less positive E° value
OHR: more positive E° value
If the RHR and OHR reactions are reversed in an electrolytic cell, what values to use when computing for E° cell?
The original values before reversing (similar lang sa pagcalculate in voltaic cell)
What does the Faraday’s Law state?
Amount of product formed by electric current = amount of electron supplied
Equation of Faraday’s Law
Q = I t = n F
Q = charge (C)
I = current ( A or C/s)
t = time (s)
n = mole of e- transferred
F = 96 485 C / mol e-
Dimensional Analysis Shortcut
mass <-> moles <-> moles of e- <-> charge <-> current
