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Electrochemistry - Coggle Diagram
Electrochemistry
Redox Reactions
Single displacement reaction
Formation & Decomposition reaction
Spontaneity
SRA higher than SOA
Non-spontaneous
E°cell < 0
Application of external electric energy
Oxidizing Agent higher than Reducing Agent
Spontaneous
Occurring without external energy
E°cell > 0
Balancing Redox equations
Half reactions
Shows the reactions of a single reactant in a reaction
Helps in balancing equations
In acidic conditions
Cannot be balanced by inspection; Only half reaction method
Write half-reactions without electrons
Balance all atoms except O₂ and H₂
Add H₂O to balance O₂ on the opposite side
Add H⁺ to balance H₂ on the opposite side
Add electrons to balance the charges
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Disproportionation
When the atoms of the same elements are both oxidized and reduced
Cell notation and Voltage
| represents phase boundary
|| represents the physical boundary
Electrical potential difference
AKA Voltage (measured with a voltmeter)
The difference between two electrodes is known as cell potential
Standard cell potential (E°꜀ₑₗₗ)
Concentration of electrolytes
Temperature
Air pressure
Nature of oxidizing and reducing agents
1atm → 101.325kPa
25°C → 273.15K
1.0 M
E°cell = E°cathode - E°anode
Hydrogen Half cell
defines the other half-cell's potential
E° = +0.00 V
Chlorine anomaly
Oxidation
The loss of electrons in a compound in a reaction
Reduction agent
loses electron
are oxidized
Reduction
The gain of electrons in a compound in a reaction
Oxidation agent
gains electrons
are reduced
Oxidation numbers
The number (not actual charges) given to an atom in a compound
The sum of oxidation numbers must equal the net charge of the molecule
All atoms in elements
0 as the oxidation number
Hydrogen in all compounds
+1 as the oxidation number
Hydrogen in hydrides
-1 as the oxidation number
Oxygen in all compounds
-2 as the oxidation number
Oxygen in peroxides
-1 as the oxidation number
All monatomic ions
charge on ion
Redox titrations
Titrant
Reagent that is added slowly using a burette
Usually a SRA or a SOA
Sample/Analyte
Reagent without a known concentration in Erlenmeyer flask
Endpoint
the point when the full reaction has taken place (equivalence point)
indicated with a color change
Reagant
A chemical added in a reaction
Writing a balanced equations
Write all entities in the solution
Determine the SOA and SRA
Write half-reactions for the SOA and SOA
Balance half-reactions and charges
Voltaic/Galvanic cells
Chemical → Electrical energy
Connected using an external circuit
No physical contact between reactants
Spontaneous reaction
Unwanted = Corrosion
Fe comes in contact with H₂O and O₂
Hydrated Iron (III) Oxide is known as rust
Electroplating helps in reducing corrosion
attaching a sacrificial node could protect it from corrosion
Electron flow from anode (-) to cathode (+)
Cathode
SOA is reduced here
Doesn't happen perpetually, cathode gains mass
Cations come here
Anode
SRA is oxidized here
Doesn't happen perpetually, anode loses mass
anions come here
Salt bridge
A porous cup to allow the passage of ions
Filled with spectator ions that will not react
Inert electrodes
RA and/or OA is not solid
Dissolved electrolytes or gases
Conducts electricity but isn't involved in reaction
Provides surface for redox reaction to occur
A battery is a collection of Voltaic cells in a series
Electrolytic cells
Electrical → Chemical energy
molten ionic compounds or an aqueous solution
Stoichiometry of electrochemical cells
Electron Flow
Current (I) measured in amperes (A)
Flow of electrons in a circuit
A = C/seconds
Electric charge (Q) is measured in coulombs (C)
Faraday's constant = 96, 500C /molₑ₋
nₑ₋ = Q/F = I(t)/F