Chapter 8 (CIC) and
Chapter 20 (CTCS)
• Read in CTCS Chapter 20.7,8
• Problems in CTCS: 20.63, 65, 67, 69, 71,
73
Battery
• Electrochemical
Cell
– May have several
wired together in
series or parallel
• Primary – one use
once EMF = 0
• Secondary –
rechargeable
*Stanitski, D.L.; Eubanks, L.P.; Middlecamp, C.H.;
Stratton, W.J. Chemistry in Context: Applying
Chemistry to Society, 3rd Edition, McGraw-Hill,
Boston, MA, 2000, pg 316.
Common Batteries
Type
Voltage Recharge?
Comments
Dry Cell
1.5
N
Alkaline
1.54
N
Lasts longer than drycell
Mercury
1.3
N
Small, long lasting,
disposal problems
Lithium ion
2.8
N
Reliable, long living
(10 yrs), lightweight
Lead
2.0
Y
Corrosive, heavy, long
lasting
Ni-cad/Ni-MH
1.46
Y
Cd is toxic/H now
replacing Cd
Lead Acid Battery
PbO2(s) + HSO4-(aq) + 3H+(aq) + 2e- PbSO4(aq) + 2H2O(l)
Pb(s) + HSO4-(aq)  PbSO4(aq) + H+(aq) + 2ePbO2(s) + Pb(s) + 2HSO4-(aq)+2H+(aq)PbSO4(aq)+2H2O(l)
K=
1
2
 HSO4   H 

  

+
2
• So, E is independent of Pb or PbO2 concentrations
• What is the voltage on each cell? There are a total
of 6 cells in a standard car battery
Battery Technology Needs
Improvement (Quickly)
• California will require 10% of all cars sold in
’03 to be ZEV
– Automakers fined $5K for each vehicle over 90%
– No CO2, CO, SOx, NOx, O3, particulate matter
• Currently, Pb-storage electric cars travel 90 mi
and recharging is needed every 3 hrs
– Batteries need replacement after 25-50 K mi
– Need 220 V chargers ($2K)
– Car costs ~$34K
• All cars by 2007 in LA basin to be converted to
“clean” power
• Energy has to come from somewhere! (power
plants – 40% efficient)
– Release CO2, CO, SOx, NOx, O3, particulate matter
• Calculations show an increase in SO2, NOx, but
a 50% decrease in CO2
• Costs are $2.50/100 mi for electric and
$6.50/100 mi for gasoline
• Ni-H battery allows
– 15 min recharge time
– 175 mi before recharge needed
– Batteries last the lifetime of the car
• CA (and NY and MA) may want to consider a
compromise for 2007 using the hybrid cars
currently available
• Hybrid car uses a Ni-H battery and consumes
50% gas (thereby releasing 50% CO2)
• Gets 66 mpg
• Charges batteries by transferring Kinetic Energy
of the car from the brakes through a generator
• Currently being sold for ~$18-20K (little profit
here)
Photovoltaics
• Ultimately move toward Solar cells
• Currently used on satellites, Hwy signs, street
lights, etc.
• Sunlight must move e- to create electricity
• Remember that visible light makes e- jump!
• In Si, 1.8 x 10-19 J/photon are required to
release an e- from a bond
– λ = 1100 nm (visible light is 350 – 700 nm)
• Si must be 99.999% pure
• Source is SiO2
• Efficiencies are 10 – 20%
Si Semiconductor
Doped Semiconductors
n-type
p-type
*Stanitski, D.L.; Eubanks, L.P.; Middlecamp, C.H.; Stratton, W.J. Chemistry in Context:
Applying Chemistry to Society, 3rd Edition, McGraw-Hill, Boston, MA, 2000, pg 323-4.
Doped Semiconductors
• Introduction of 1 ppm Ga gives only 7 earound it yielding a “positive hole”
• Introduction of 1 ppm As gives 9 e- around
it yielding a “negative hole”
• These holes will increase conductivity
• This allows light of longer wavelengths to
move e-
Costs
• In 1974, photovoltaics cost $3/kw-hr
• By 1998 the cost was $0.28/kw-hr
• This compares to a cost of about $0.07/kwhr for fossil fuels
• If no gains were made on semiconductors,
the US could get all electrical needs by a
photovoltaic generating station the size of
NJ (85 mi2)
Corrosion
• M + O2  MxOy
Fe  Fe2+ + 2eE = -0.44
V
O2 + 4H+ + 4e-  2H2O
E = 1.23 V
2Fe + O2 + 4H+  2Fe2+ + 2H2O E = 0.79 V
• Fe2+ will ultimately be converted to Fe3+
Fe2+  Fe3+ + eE = -0.771
V
Cures for Corrosion
• Cover with paint
– If you get a scratch in paint, it will still rust
• Cover with Zn (what is the Eº?)
– If coating is scratched, the Zn still gets oxidized
• Alloyed with 18% Cr
– If you get a scratch in surface, the underlayer will
still rust
• You can use a sacrificial anode (Mg) for buried
pipes (Mg  Mg2+ + 2e-)
– Simply done by attaching (conductively) a piece of
Mg metal to your metal of interest