Rxn Mechanisms

Good day. A few terms from the day:
reaction mechanism (series of simple chemical equations that can be added together (Hess's Law style) to produce the overall, observable reaction
elementary step (individual step of a mechanism, typically involves one or only a few molecules); molecularity identifies the number of reactant particles (1 = unimolecular, 2=bimolecular, 3=termolecular)
reaction intermediate - temporary product, product made in one elementary step and used up in subsequent elementary step
rate determining step - the slowest elementary step of a mechanism (not always the first of a mechanisms) - direct relationship with the rate law

The link below is another excellent little tutorial. Once again there are some practice questions (with answers).
http://www.wwnorton.com/college/chemistry/gilbert/tutorials/interface.asp?chapter=chapter_14&folder=mechanisms

or try the same link with a slightly different url
http://www.wwnorton.com/college/chemistry/gilbert/tutorials/interface.swf?chapter=chapter_14&folder=mechanisms

I hope that you take the 5 or 10 minutes to look at the link. I thought that there were some great little gems tucked away in that puppy.

Next up:
-review for test
-reaction mechanisms lab (bring a timing device)

A few leftover mole day jokes: Why did the mole cross the road? [Because the chicken was busy.] Why are moles bad at counting? [Because they only know one number.] Why are moles always on their cell phone? [Because they love moleble devices.] Can you tell which one I made up myself?

Potential Energy Diagrams

Be aware of the terminology.
heat of reaction, activation energy forward, activation energy reverse, activated complex

The following are a few examples of potential energy diagrams:
(1) Endothermic shown below

source:http://bilbo.chm.uri.edu/CHM112/lectures/Image90.gif(Oct 21,2009)

(2) Exothermic shown below

source:  https://chemistry.twu.edu/tutorial/activation-energy.gif  (Oct 21, 2009)

A nice link. Again with practice questions and answers.

http://www.saskschools.ca/curr_content/chem30_05/2_kinetics/kinetics3_2.htm

Potentially, you may find the following jokes amusing. Why did the fish cross the road? [Somebody threw it.] What sea animal can be adjusted to play music? [A tune-a fish.] What lies at the bottom of the sea and shakes? [A nervous wreck.]

Rate Laws II

Good day rate law questioners

The following link is quite a nice one. At the end of it there are some practice questions with answers.

http://www.wwnorton.com/college/chemistry/gilbert/tutorials/interface.asp?chapter=chapter_14&folder=reaction_order

or try
http://www.wwnorton.com/college/chemistry/gilbert/tutorials/interface.swf?chapter=chapter_14&folder=reaction_order
[Both represent the same link, the first one has a few letters changed so that it will work at school]

Next up PE Diagrams - something like:

Source: http://irina.eas.gatech.edu/lectures/lec6fig4.jpg (October 21, 2009)

That is all for today kiddies. Finally, fish funnies: Why are fish so smart? [Because they live in schools.] Why is it so easy to weigh fish? [Because they have their own scales.] What is the easiest way to catch a fish? [have someone throw it at you.] Finally. What happens when you throw a green rock into the Red Sea? {It gets wet.]

Rate Laws

A few exponential questions to start:
(1) 2, to what exponent is 4?  [Answer 2]
(2) 2, to what exponent is 8? [Answer 3]
(3) 2, to what exponent is 2? [Answer 1]
(4) 2, to what exponent is 1? [Answer 0]

The above is the kind of mathematical thinking that is required for this next portion of the unit.

After the rate law lesson you should be able to produce a specific rate law similar to the following general rate law:
rate = k [A]x [B]y [C]z
where k is a constant with its own units and x, y, z are all exponents (The link below shows the format with all its exponential glory.)

The following link will provide some additional insight into rate laws. I would not spend a great deal of time focusing on the various graphs. The interpreation of the chart data to arrive at a rate law is where the lesson on rate laws ends up.
http://www.science.uwaterloo.ca/~cchieh/cact/c123/coneffec.html

That is all for today. Q: What did the ocean say to the penguin? A: Nothing it just waved. Q: How does a penguin build its house? A: Igloos it together.