Intersection 12

Batteries

Gatorade

Dental Voltaic Cell

From: Moore, Stanitski, and Jurs Chemistry: The Molecular Science 2nd Edition/

p.941

Batteries

• Factors in battery design:

CostWeightPotentialRechargeabilityEnvironment

BatteriesPrimary Cells

non-reversible, non-rechargeable electrochemical cell

"dry" cell & alkaline cell 1.5 v/cell

mercury cell 1.34 v/cell

fuel cell 1.23v/cell

BatteriesSecondary Cells

reversible, rechargeable electrochemical cell

lead-acid (automobile battery) 2 v/cell

NiCad 1.25 v/cell

“Flash Light” Batteries

Primary Cells

"Dry" Cell

Zn(s) + 2 MnO2(s) + 2 NH4+

Zn+2(aq) + 2 MnO(OH)(s) + 2 NH3

Alkaline Cell

Zn(s) + 2 MnO2(s) ZnO(s) + Mn2O3(s)

Leclanche “Dry” Cell

Mercury BatteryPrimary Cells

Zn(s) + HgO(s) ZnO(aq) + Hg(l)

Fuel Cells

anode

2( H2(g) + 2 OH-(aq) => 2 H2O(l) + 2 e-)

cathode

O2(g) + 2 H2O(l) + 4 e- => 4 OH-(aq)

Picture from: http://www.bpa.gov/Energy/N/projects/fuel_cell/education/fuelcellcar/

Lead-Acid(Automobile Battery)

Pb(s) + PbO2(s) + 2 H2SO4 2 PbSO4(s) + 2 H2O

charging batteryrequires electricity

discharging batteryrequires electricity

2 v/cell thus 12 volt battery = 6-2 volt cells

Secondary Cell

Lead-Acid(Automobile Battery)

Nickel-Cadmium (Ni-Cad)

Secondary CellCd(s) + 2 Ni(OH)3(s) Cd(OH)2(s) + Ni(OH)2(s)

Lithium Batteries

• Lithium batters (developed in 1970; used in watches, pacemakers, etc.)

• The 4-volt lithium battery, which has up to 33 percent higher energy density and 60 less weight than a nickel-metal hydride battery of the same size, has made possible the miniaturization of the current generation of electronic devices

Lithium chemistry

• What is the ½ reaction involving lithium?

• Is this a reduction or oxidation reaction?

• Does it take place at the anode or cathode?

The other ½ of the battery:

• Co+3 + e- Co+2 (+1.92 V)

• What is the standard potential of the cell?

[Li Li+ + e- (+ V)]

• A lithium battery has a potential listed at 4V. Does this differ from the number you calculated? Why?

Alternative Anodes

• Which elements would you predict to have oxidation potentials similar to lithium? (no peeking at the table of standard reduction

potentials!)

Is what way is lithium preferable to these elements?

Alternative Cathodes

• There are other reduction potentials that rival that of Co+3 Co+2. What are they?

• Why aren’t they being used in conjunction with lithium to build a battery with higher potential?

Table of Standard Reduction Potentials

Eo Eo

F2 + 2e- --> 2F- 2.87 Fe3+ + 3e- ---> Fe -0.04Co3+ + e- --> Co2+ 1.80 Pb2+ + 2e- ---> Pb -0.13Cl2 + 2e- ---> 2Cl- 1.36 Ni2+ + 2e- ---> Ni -0.25O2 + 4H+ + 4e- -> 2H2O 1.23 Co2+ + 2e- ---> Co -0.29Hg2+ + 2e- ---> Hg 0.85 Cr3+ + e- ---> Cr2 -0.40Ag+ + e- ---> Ag 0.80 Fe2+ + 2e- ---> Fe -0.41I2 + 2e- ---> 2I- 0.54 Zn2+ + 2e- ---> Zn -0.76Cu+ + e- ---> Cu 0.52 Mn2+ + 2e- ---> Mn -1.182H+ + 2e- ---> H2 0.00 Al3+ + 3e- ---> Al -1.66

Other commercially viable batteries

• Besides cobalt, two other reduction reactions used in lithium batteries are shown below. What is the potential of these batteries?

• Fe+2 Fe

• ½ I2 I-

Other cathode reactions being explored

• Al and Mg are also being explored as materials for the cathode. What are the advantages and disadvantages of these materials?

The Electrochemical Cell

• Sketch the complete electrochemical cell.

• An organic electrolyte solution is used. Why?

Gatorade®

• Origin /

Pictures courtesy of: http://www.gatorzone.com/stevespurrier/ and http://www.gssiweb.com/pdf/perfseries.pdf

Quote courtesy of: http://chemcases.com/gatorade/gatorade03.htm

“It was the summer of 1965. On the practice fields of Gainesville, Florida University coach Ray Graves watched his athletes walk slowly through their drills. To the side, his quarterback, Steve Spurrier - a young man with enormous talent that Graves rightly expected would one day win the Heisman Trophy - stood alone and tossed ball after ball through a tire suspended 30 yards away.”  

"Are they drinking water?" the team doctor asked.

"Well, we have water for them. Yeah, they drink a little bit of it." The coach said.

"What else do you do?" the doctor asked.

"We make them take salt tablets because they sweat so much salt.“

"Do you give them juice? Orange juice?" the doctor said."They guzzle the juice when we give it to them. Then they throw up. Same thing with soft drinks. They get cramps and get sick.“

"We think we can help, coach. We think we can make you a drink the team will like and that will let them tolerate the heat," said the team doctor. His name was Dana Shires. He was then a young physician working as a research fellow in the laboratory of Dr. Robert Cade.

Text courtesy of: http://chemcases.com/gatorade/gatorade03.htm

Body Functions

• We expel carbon dioxide produced in oxidation through respiration.

• We eliminate urea through urination. • We lose water by urination, by perspiration, and as a

component of expelled gases through respiration. • The sweat passing through the membrane of the skin

contains salts from the body and deposits them on the surface of the skin.

• Heat buildup is controlled by evaporation of water from the surface of the skin and by the expiration of water vapor through breathing.

Humidity Hurts

• Why would humidity affect performance?

• How much energy does it take to evaporate a pound of water that is body temperature (98.6oF)?

– Cwater = 75.3 J/(moloC) – oC = (5/9)(oF – 32)– ΔHvap water = 40.79 kJ/mol– 1 lb = 453.6 g

Consequences of Dehydration

• Prof. Coyle of the University of Texas writes, "Even a slight amount of dehydration causes physiological consequences. For example, every liter (2.2 lbs) of water lost will cause heart rate to be elevated by about eight beats per minute, cardiac output to decline by 1 L/min, and core temperature to rise by 0.3o C when an individual participates in prolonged exercise in the heat."

Salt and Dehydration

• The salt concentration of blood is about 9g/L.  The fluid that passes through the skin as sweat contains a lower concentration of salts; five liters of fluid loss would carry away about 14 g of sodium chloride (not 45 g.)

• The kidneys would respond to the increased salt concentration by excreting a concentrated, dark-colored urine in order to decrease the salt content in the blood.

• The blood cells will shrink, the volume of blood decreases, blood pressure drops. In extreme cases, the combination of low blood pressure and low blood volume and can lead to catastrophic heat stroke.

• The common wisdom of the 1960s was that exercising athletes should take salt tablets. But they were not encouraged to drink fluids. The salt drew fluid from the body into the intestines.

Fluid Uptake

• Dr. Malawer told the Florida group he had studied the rate of absorption of water through the wall of the small bowel in human volunteers. (Fluid exchange occurs through the wall of the small bowel, not the stomach. The stomach serves only as a container.)

• Dr. Malawer's tests showed the fastest rate of transfer of water through the semipermeable membrane of the bowel occurred with a solution that was isotonic -- had the same concentration of particles -- with the body. A solution of salts and glucose of the same concentration as the extracellular fluids showed the highest rate of uptake through the small bowel.

Gatorade® ingredients

• Water –hydration• Citric acid (tartness)• Sucrose• Glucose-fructose• Salt• Flavoring• Brominated vegetable oil• Mono potassium phosphate

6% CarbohydrateOJ and soft drinks are 10% complex sugars

HOO

H

H

HO

H

O

OHH

CH2

H

OH

O

H2C

OHHO

H2C

OH

OH

H

H

OH

sucroseHf = -2226.1 kJ/mol

OCH2HO

HO

CH2

OH

OH

H

H HO

fructoseHf = -1240 kJ/mol

HOO

H

H

HO

H

OH

OHH

CH2

H

OH

glucose

ΔHf Glucose

• The only ΔHf missing is glucose. 5.26 g of glucose C6H12O6 are burned in a calorimeter containing 1 L of water at 20.3oC. The final temperature of the water is 29.0oC. Find the ΔHf of glucose.

• Cwater = 75.3 J/(moloC)

Which of the Gatorade®

ingredients are acidic?• Water• Citric acid • Sucrose• Glucose-fructose• Salt• Flavoring• Brominated vegetable oil• Mono potassium phosphate

Acids – weak or strong?

• Citric acid

• Mono potassium phosphate

• Write out their equilibrium expressions as appropriate.

Gatorade® pH

• The pH of Gatorade is 2.95. If the citric acid were solely responsible for the pH, what would its initial concentration be?

• Ka1= 7.1 x 10-4 

Gatorade® pH

• How would the addition of sodium citrate affect the pH of the solution?

Gatorade® Flavoring

H

O

citral

The lemon flavoring used by Gatorade® is citral.

Brominated vegetable oil is used as a flavor emulsion.

Explain.

O-

OBr

Br

Brominated vegetable oil

Original Sweetness

• Sodium cyclamate was shown to cause bladder cancer in mice

• Replaced with fructose

The when and how much:

• Drink 17-20 oz 1+ hr ahead of exercise

• 7-10 oz right before exercising

• 7-10 oz every 15 minutes

• 20 oz for every pound lost after exercising

Testing out Gatorade®

• Dr. Shires brought the new beverage to the Florida freshman on their practice field, late summer 1965 .

• Can you just give the new drink to the players?– Was the product toxic? – Had it been properly tested in the laboratory on animals before it

was introduced for human consumption?   – It comes out of a well respected research group.– What if someone gets sick?– The varsity squad is set for a stellar season, but the freshman

team…– Do you need outside approval?

Conducting Medical Experiments

• Did the product work? 

– The athletes reported they felt stronger.  – Was it cooler weather?– No control group.– No objective or quantitative measures. – How do you know if you succeeded or failed?

Who Owns Gatorade®?

• (1.5 billion a year in sales)

• Dr. Cade offered rights to UF and USA

• Stokely-VanCamp got production rights from Dr. Cade

• Ended up in court.