Chapter 12- Electrochemistry Flashcards
Location of oxidation and reduction
AN OX (anode- oxidation) and RED CAT (cathode- reduction)
What is an electrochemical cell and name 3 types
Contained system where oxidation-reduction reactions occur. Ex: galvanic (aka voltaic)- spontaneous, electrolytic- nonspontaneous, and concentration-spontaneous
Electromotive force (EMF)
Voltage or electrical potential difference of the cell. If + then spontaneous release of energy. If - then nonspontaneous absorption of energy.
Movement in electrochemical cells
Movement of electrons- from anode to cathode. Current- from cathode to anode.
Relationship between free energy and electromotive force
Always have opposite signs
Electrolytic cells
Nonspontaneous and require energy input (🔺G = +) and thus type of redox reaction driven by an external violate source is called electrolysis (chemical compounds are decomposed)
Faradays constant (one faraday)
1 F = 96,485 C (on MCAT round number to 10^5 C/mol e-)
Electrodeposition equation. Helps determine number of miles of element being deposited on a plate.
mol M = It / nF (Moles of Metal, It is Not Fun)
Concentration cell
Type of galvanic cell. Spontaneous. Chemically identical electrodes. Curren generated is as a fiction of a concentration gradient.
Rechargeable batteries
Can function as high galvanic and electrolytic cell.
Positive and negative of galvanic cells
Anode- negative
Cathode- positive
Positive and negative of electrolytic cells
Anode- positive
Cathode- negative
Because it requires an external source to reverse the charge of an electrolytic cell
Reduction potentials for galvanic cells
More + reduction potential = cathode. Less + reduction potential = anode.
Reduction potentials for electrolytic cells
More + reduction potential = anode. Less + reduction potential = cathode.
Solving for emf based on reduction potentials
Ecell = Ecathode - Eanode
(-) answer means nonspontaneous thus electrolytic
Relationship between Gibbs free energy and emf
🔺G = -nFEcell
n- number of moles of e- exchanged
Nerst equation (used when conditions deviate from standard conditions)
Ecell = Ecell -0.0592/n (log Q)
Q- reaction quotient
Combination of 2 🔺G expressions
nFEcell = RTln(Keq)
Calculating log or ln rules…
If the log is…
+ when greater than 1
- when less than 1
0 when equal to 1
Change in Gibbs free energy of an electrochemical cell with varying concentrations
🔺G = 🔺G* + RT ln(Q)
🔺G* under standard conditions
Electrolysis
External voltage source drives this nonspontaneous oxidation-reduction reaction
What is the only thing E*cell is dependent on?
The identity of the electrodes
What is reduced in electrochemical cells?
Cathode
What is reduced in galvanic cells?
More positive reduction potential
