Electrochemistry Flashcards
Electrochemistry
Chemistry concerned with electron exchange and redox chemistry
Reduction
Gain of electrons
Oxidation
Loss of electrons
How do you get oxidation state/number?
1.) one ion, state = charge
2.) For ions with multiple elements, the states must equal the overall charge
- if it contains these ions, it can affect the
charge
priority increases from bottom to top
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F -1
Group 1/2 metal +1/+2
H +1
O -2
Halogens (Cl, Br, I) -1
Oxidizing agent
Causes something else to oxidize while the agent undergoes reduction
Reducing agent
Causes something else to reduce while the agent undergoes oxidation
Half reaction
Half of a whole reaction showing redox
How to balance a reaction given 2 half reactions?
Multiply so electrons completely cancel out and add rxns together
How to get half reactions?
- Write out net ionic
- Split reactions apart
- Balance moles
How can you balance half reactions and redox reactions?
- Balance half rxns themselves
- Add H2O to balance out O atoms in half reactions
- Add H+ on the other side to balance out the H2O
- Add electrons to either side so the charges can be the same (not 0) on each side
- Add reactions together and multiply so electrons cancel out
How can you balance half reactions and redox reactions in a basic solution?
1) Balance as if in acidic
2.) Add same amount OH as H plus
3.) The OH and H combine to water, and the 14OH adds as normal to the other side
4.) The waters on each side cancel out
How is a current generated?
As a redox reaction happens
Battery
Galvanic/Voltaic cell (spontaneous)
Electrolytic cells
Two half rxns that occur nonspontaneously but are forced to
E oxidation =
-E reduction
How can you decide if something is an oxidation or reduction reaction?
The less positive of the two half rxns will oxidize
How to build a galvanic cell?
- Electrons go from anode to cathode
- Positive ion in the salt bridge go to the cathode and the negative ion goes to anode
- mass anode decreases and conc increases, mass cathode increases and conc decreases; no pH change
Cathode
reduction half cell
Anode
oxidation half cell
Electrode
Conductive surface in the half call, the physical solid in the solution
Cell notation
Abbreviated form of electrochemical cell
electrode(s) - chemical anode(aq) – chemical cathode (aq) - electrode(s)
E cell equation (standard)
(RT/nF)(lnK)
G cell equation (standard)
-RTlnK
Concentration cells
A galvanic cell built on half cells with the same substances
