Electrochemistry Flashcards
Oxidation number of hydrogen in most compounds
+1
Oxidation number of oxygen in most compounds
-2
Oxidation number of fluorine in any compound
-1
Elemental species have an oxidation number of
0.
Elemental ions have oxidation numbers
equal to their charge.
Ex. In Fe3+, iron has an oxidation number of +3
All oxidation numbers of each individual atom in a compound must add up to
the charge on the compound.
Group 1A metals oxidation state in all compounds
+1
Group 2A metals oxidation state in all compounds
+2
Meaning of LEO says GER
Loss
Electrons
Oxidized
Gain
Electrons
Reduced
Oxidation always occurs at the
anode. (Red cat / an ox)
Reduction always occurs at the
cathode. (Red cat / an ox)
Electrons flow in what direction in an electrochemical cell?
Anode to cathode (FAT Cat)
Which electrode is sometimes found to lose mass in an electrochemical cell?
Anode (FAT Cat)
Which electrode can have matter accumulate at the electrode?
Cathode (FAT Cat)
Cations travel through the salt bridge to which half-cell?
Cathodic
Anions travel through the salt bridge to which half-cell?
Anodic
How does the salt bridge complete the circuit in an electrochemical cell?
Ions travel through salt bridge
Note: Electrons do NOT freely travel through the salt bridge.
When you reverse a reaction, what do you do to E°?
Change the sign (pos to neg or neg to pos)
When you change the coefficients of a reaction, what happens to E°?
NO CHANGE
Formula for E°cell from half-reaction potentials
E°cell = E°red + E°ox
When adding half-reactions, what has to happen?
Electrons must cancel out
For a galvanic/voltaic cell, the half-reaction with the more positive E*°red will occur at the
cathode.
For a galvanic/voltaic cell, the E*°cell must be
positive.
When calculating ΔG°rxn from E°cell or vise-versa, ΔG*°rxn must be in
J NOT kJ.
When calculating ΔG°rxn from E*°cell or vise-versa, n is the
moles of electrons transferred per mole of rxn.
What is considered to be standard conditions?
Gases at 1 atm partial pressure
Concentrations at 1 M
Temperature at 298 Kelvin
At non-standard conditions, if Q is ______ than one, E is less than E°.
Greater
At non-standard conditions, if Q is less than one, E is _______ than E°.
Greater (more reactants, so more charged)
As Q approach K for a galvanic/voltaic cell, what happens to the voltage?
The voltage approach zero
Equilibrium is where batteries go to die!
K for galvanic/voltaic cells reactions is usually
a huge number (very product favored and goes to completion).
