1. Chemistry SM-1232 Week 12 Lesson 2
Dr. Jesse Reich
Assistant Professor of Chemistry
Massachusetts Maritime Academy
Spring 2008

2. Class Today A few wikis started!!! GET ON IT! At least start the page.
Wiki quiz and homework due Wednesday. No exceptions.
Start Chapter 18
Test on chapter 15 and 16 Friday

3. Batteries!
Electrical current is the flow of electrons (negatively charged particles).
Redox reactions require the flow of electrons, and we can use these reactions to make current!

4. Electrochemical Cell

5. Half Cells Zn is placed in Zn(NO3)2 to form a half cell
Cu is placed in Cu(NO3)2 to form a half cell

6. Electrochemical Cell
Anode is the strip where oxidation occurs, labeled with a negative sign
Cathode is the strip where reduction occurs and is labeled positive

7. The Bridge
The bridge is a salt bridge that allows ions to flow to balance out the chares that are being generated at the anode and the cathode

8. Galvanic (Voltaic) Cells
Cells that spontaneously produce electrical current are called Galvanic or Voltaic cells.
Water is analogous. The amount of water that flows through a river determines the river current. The amount of electrons that flow determine the electrical current.
Gravity forces water down hill to reduce potential energy. Voltage forces electrons from one atom to the next to reduce pot. En.

9. Dead Batteries
You saw this in lab. The metal actually dissolves into solution. The metal containing the electrons has been transformed and no longer has those electrons. When all the metal is used up the battery dies. Rechargable batteries reverses the reaction and solid metal reappears.

10. Dry Cell Batteries Dry because there is no water.
Zinc  Zn2+ + 2e- (oxidation, anode)
2MnO2(s) + 2NH4+ + 2e-  Mn2O3(s) + 2NH3(g) + H2O(l)
(cathode reduction)
Alkaline battery:
Zn(s) + 2OH-(aq)  ZnOH2(s) + 2e-
2MnO2(s) + 2H2O + 2e-  2MnO(OH)(s) + 2OH-(aq)

11. Dry Cell

12. Lead-Acid Storage Batteries (car)

13. Car Batteries 6 different cells each that have 2 volts
Pb(s) + SO42-  PbSO4(s) + 2e-
PbO2(s) + 4H+ + SO e-  PbSO4(s) + 2H2O
Putting current through in the opposite direction reverses the reaction and Pb(s) is regenerated as is PbO2. So, the forward reaction can repeat later.

14. Fuel Cells

15. Fuel Cell H2(g) + 4(OH)-  4H2O + 4e- O2(g) + 2H2O + 4e-  4OH-
Go ahead and combine them. What product do we make? Which is the reduction, which is oxidation? Which side will be the anode? Cathode? Which side gets the positive sign? Which gets the negative sign?

16. Silver Plating

17. Organic Chemistry
O-chem is serious business. Basically everything in the pharmaceutical world is based on organic chemistry.
There is a big split between organic chemistry and inorganic chemistry.
Organic chemistry found in living organism typically contains C, H, O, N, S, P.
Inorganic chemistry is the combination of metals with non-metals.

18. Smells
Anything that has a smell has at least a small amount of an organic compound that has vaporized. When you breathe it in your body detects that organic compound and you react to it.
Things that are good for you typically smell good. Things that are bad for you typically smell bad. Yeah, evolution!

19. Carbon Based Lifeforms
Life on this planet requires 1 element in particular. Carbon. Carbon is central to all of the living organisms on earth.
Carbon will always form 4 bonds. Not more and not less in organic chemistry.

20. Valence Electron & Octet Rule Reminder
Group 1-8 elements have the same number of valence electrons as the group number.
Octet rule states that these elements want to lose electrons to get down to 0 valence electrons or gain electrons to get up to 8 (H and He gain up to 2 instead of 8).

21. VSEPR reminder If carbon makes 5 bonds you did something wrong!
If carbon makes 4 bonds it will form a tetrahedral arrangement
If carbon makes 3 bonds it will form a trigonal planar arrangement
If carbon makes 2 bonds it will form a linear arrangement

22. Hydrocarbons One of the simplest organic compounds.
Only made up of 2 elements: hydrogen and carbon
Hydrocarbons take a wide variety of forms anything from natural gas, propane, butane, gasoline, diesel, jet fuel, wax, and jelly.

23. Hydrocarbons (names and structural formulas)
Count the hydrogens!
What’s the formula for number of hydrogens relative to carbons?

24. Unsaturated Hydrocarbons
We’re going to put in one double between the last and the second to last carbon. Draw it, add in hydrogens so that every carbon has four bonds. Compare hydrogens to carbons.
As a group, hydrocarbons with double bonds in them are called alkenes.

25. Unsaturated Hydrocarbons
We’re going to put in one triple between the last and the second to last carbon. Draw it, add in hydrogens so that every carbon has four bonds. Compare hydrogens to carbons. What’s the formula now?
As a group hydrocarbons with triple bonds in them are called alkynes.

26. Aromatic Hydrocarbons: a subset of unsaturated
There is a special group called aromatic. They used to be known for their distinct odors which is why they are “aromatic.” Now we know it has to do with containing carbons in a special ring. We’ll talk about this more later.

27. Properties Alkane Boiling Point (C) Methane -162 Ethane -89 Propane
-42
butane -1
pentane 36
hexane 69
Heptane 99
Octane
126

28. Uses Number of Carbons Phase Major Use 1-4 Gas
Heating and cooking fuel
5-7
Low boiling liquid
Solvent, gasoline
6-18
liquids
gasoline
12-24
liquid
Jet fuel, kerosene
18-50
High boiling liquid
Diesel fuel, lubricant, heating oil
50+
Solid
Petroleem jelly, paraffin wax
1,000+
solid
Plastics, polyethylene and polypropylene

29. Write the molecular formula

30. Write a condensed structural formula
Anytime you see a CH3 you have to write it. If you have 1 CH2 group you will write that. If you had 5 CH2 groups you will write (CH2)5.

31. Isomers
There are 5 ways to draw a molecule that has 6 carbons that are distinct from each other. Using only carbon to start try to draw them. Write the formula for each one. Define an isomer (be sure to use the terms structural formula and molecular formula).

32. Read all of chapter 16
Test on Friday.
Quiz due today. HW on Friday.