Download Electrochemistry

Honors Chemistry
Electrochemistry
Electricity:
 The transfer
or movement
of electrons.
Electrochemistry:
Electrical applications
of redox reactions
Redox:
Zn+CuSO4→ZnSO4 +Cu
• Zn →
•
2+
Cu
2+
Zn
+
−
2e
+
−
2e
→ Cu
Electrochemical
Cell:
device that uses
redox reactions to
produce or use
electricity.
•Galvanic (voltaic) cells
are spontaneous reactions
•Electrolytic cells are not
spontaneous
Electrodes:
a
metal or graphite
surface on which
oxidation or reduction
can occur.
Anode:
electrode
at which
oxidation occurs.
negative electrode for
voltaic rxns.
Cathode:
electrode
at which
reduction occurs.
positive electrode
for voltaic.
Half-Cell:
Container
in which a
half reaction of a
redox reaction occurs.
Salt Bridge:
a
tube of an electrolyte
that connects two voltaic
half-cells allowing ions to
move between
compartments
without mixing.
Notation:
anode ∣an. soln ∥ cath. soln ∣ cathode
Mg(s) ∣
2+
Mg
(aq)
∥
2+
Cu
(aq) ∣
Cu(s)
Notation for:
Zn+CuSO4→ZnSO4 +Cu
2+
−
• Zn → Zn + 2e
2+
−
• Cu + 2e → Cu
Zn|
2+
Zn
||
2+
Cu
|Cu
Cell Potential (Ecell ):
 difference in electric
potential energy
between 2 electrodes
of a voltaic cell.
Voltage (volts): units
for cell potential
Electrode Potential:
Reduction
potential is the
tendency for a reduction
half-reaction (cathode).
Oxidation potential is the
tendency for an oxidation
half-reaction (anode).
Standard Cell Potential
E°cell
Standard conditions:
 [ ion ] =1 M
 P = 1 atm.
 T = 25°C
Cell Potential (Ecell )
Sum
of electrode
potentials
E°cell = E°red + E°ox
E°cell=E°red − E°red of ox
Standard Reduction Potentials
Problem: (See p.664)
Calculate
E°cell produced
by a voltaic cell with a
2+
nickel electrode in Ni
solution and a silver
electrode in solution of
+
Ag ions.
Problem:
Calculate
the voltage
produced by a voltaic
cell with an Al
3+
electrode in Al
solution and an iron
electrode in a solution
2+
of Fe ions.
Electrolysis:
Use
of electrical
energy to bring
about a chemical
reaction.
Electrolytic Cell:
an
electrochemical
cell where electrical
energy drives
nonspontaneous
reactions.
Electroplating:
depositing
one
metal on another
by use of electric
current.