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, 3 rd Edition, McGraw-Hill, Boston, MA, 2000, pg 316.

3. Common Batteries TypeVoltageRecharge? Dry Cell1.5N Alkaline1.54N Mercury1.3N Lithium ion2.8N Lead2.0Y Ni-cad/Ni-MH1.46Y Comments Lasts longer than dry- cell Small, long lasting, disposal problems Reliable, long living (10 yrs), lightweight Corrosive, heavy, long lasting Cd is toxic/H now replacing Cd

4. Lead Acid Battery PbO 2 (s) + HSO 4 - (aq) + 3H + (aq) + 2e -  PbSO 4 (aq) + 2H 2 O (l) Pb (s) + HSO 4 - (aq)  PbSO 4 (aq) + H + (aq) + 2e - PbO 2 (s) + Pb (s) + 2HSO 4 - (aq) +2H + (aq)  PbSO 4 (aq) +2H 2 O (l) So, E is independent of Pb or PbO 2 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 CO 2, CO, SO x, NO x, O 3, 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 CO 2, CO, SO x, NO x, O 3, particulate matter Calculations show an increase in SO 2, NO x, but a 50% decrease in CO 2 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% CO 2 ) 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 SiO 2 Efficiencies are 10 – 20%

9. Si Semiconductor n-type Doped Semiconductors p-type *Stanitski, D.L.; Eubanks, L.P.; Middlecamp, C.H.; Stratton, W.J. Chemistry in Context: Applying Chemistry to Society, 3 rd 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 mi 2 )

12. Corrosion M + O 2  M x O y Fe  Fe 2+ + 2e - E = -0.44 V O 2 + 4H + + 4e -  2H 2 O E = 1.23 V 2Fe + O 2 + 4H +  2Fe 2+ + 2H 2 O E = 0.79 V Fe 2+ will ultimately be converted to Fe 3+ Fe 2+  Fe 3+ + 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  Mg 2+ + 2e - ) –Simply done by attaching (conductively) a piece of Mg metal to your metal of interest