Chapter 8 (CIC) and Chapter 20 (CTCS)

1. Chapter 8 (CIC) and Chapter 20 (CTCS) • Read in CTCS Chapter 20.7,8 • Problems in CTCS: 20.63, 65, 67, 69, 71, 73

2. 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.

3. Common Batteries

4. Lead Acid Battery PbO2(s) + HSO4-(aq) + 3H+(aq) + 2e-PbSO4(aq) + 2H2O(l) Pb(s) + HSO4-(aq) PbSO4(aq) + H+(aq) + 2e- PbO2(s) + Pb(s) + 2HSO4-(aq)+2H+(aq)PbSO4(aq)+2H2O(l) • 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

5. 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

6. 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

7. 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)

8. 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%

9. 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.

10. Doped Semiconductors • Introduction of 1 ppm Ga gives only 7 e- around 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-

11. 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/kw-hr 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)

12. Corrosion • M + O2 MxOy Fe  Fe2+ + 2e- E = -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+ + e- E = -0.771 V • Acid rain should help promote corrosion

13. 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