"The Very Unlikable Fritz Haber"

This is a short cross-post from Dr. Shane Street's UAGenChem blog, updating us on the man Fritz haber, who I discussed a few posts back (Haber Synthesis of Ammonia).

I'll summarize that he was not a nice man in general and leave the main discussion to Dr. Street's blog post:

http://uagenchem.blogspot.com/2013/02/the-very-unlikable-fritz-haber.html

+Joseph Meany

Hydronium

So the Hydronium ion, the representation H3O+ of the free (solvated) protons in an aqueous acid, is an interesting concept. In 1983, a paper published in Physical Review Letters shows evidence of the free ion in the gas phase.
While the details of the paper are quite complex, it's interesting to see that the reaction of H2 and O2 will proceed through the H3O+ ion and is observable on short time scales.
Free protons!

Another bang- "Gun Cotton"

We're still working on chemical equilibrium in class, and so what better way to spice up the dry mathematics of the equilibrium equations by MORE FIRE???

Consider the following reaction, and keep in mind Le Chatelier's Principle.


Nitrocellulose Polymer. The dashed lines indicate repeating units to "infinity". Image courtesy of Wikipedia

(C6H8(NO2)2O5)n + flame ----> CO2  + H2O + CO + N2

What we see here is that a solid, the nitrocellulose is ignited and is self consumed. This quick tutorial video about the reaction shows a nice ignition flash- but notice there's no smoke nor ash! Why is this so?
All of the products of the reaction are gaseous, which means there is no solid residue to leave behind. The smoke and ash in normal fires are caused by bits of solid carbon from the paper clumping together from incomplete combustion- but the energy coming out of the nitrocellulose combustion is so great (and self-sustained) that all of the carbon gets converted into its gaseous oxides. The gasses leave the reaction area by a physical process called diffusion, which makes the equilibrium of the reaction shift to the right. Remember- removing products shifts the equilibrium in that direction!
Periodic Videos gives a great basic introduction to the cellulose molecule in the beginning and a historical perspective on the uses of nitrocellulose since it was discovered. The videos on that site are great. Note, however, that their cotton was not fully nitrated. It left behind some embers after a rather impressive flame.

A note on the nitric acid. Commercial production of this strong acid is carried out via the "Ostwald Process", which uses ammonia as a feedstock- ammonia usually obtained from the "Haber Process" that I mentioned in my last post!

https://www.youtube.com/watch?v=QQ5q9G1lHUc
http://chemistry.about.com/od/makechemicalsyourself/a/make-nitrocellulose-flash-paper.htm
http://www.periodicvideos.com/videos/mv_guncotton.htm

+Joseph Meany

Don't say I didn't tell you so!

So Dr. Vincent passed out the exams today after the low-attendance class on Friday. There was a demo and  accompanying video....but these were labeled TOP SECRET for those that were not in class so I'm not able to discuss anything about them more. Sucks to be you!

We spent the first portion of class going over the exam, and Dr. Vincent revealed to us that he's not the "Great God of Carbonation"

(The real God of Carbonation is Sauron) Image courtesy of LOTR Wiki

In fact, the soda trick was just about re-equilibrating the gas inside a can of soda to make it not spray everywhere after being shaken and squeezing the other unshaken can to make it explode upon opening. He's a fraud...but at least many in the class got the bonus question right!
We went over the exam in detail today in class...so for those that missed class- you missed out.
+Joseph Meany

http://lotr.wikia.com/wiki/Sauron

MORE HELP!

Tyler DeWitt (not related to the Adelle DeWitt of Dollhouse) is a former high school science teacher and current Ph.D. student at MIT who was recently featured at a TEDx Convention giving a talk about making science fun and engaging for students. He argues about eschewing some of the exacting jargon in typical public school science textbooks to make concepts more accessible to teens.

(Although he does look a bit like Adam Tudyk, doesn't he?) Images courtesy of Google Image Search

As a part of his vision, he (like Salman Khan) has produced a series of videos to assist students in learning different concepts from chemistry. His YouTube Channel is chock full of short, concise videos that help break down practice problems- especially for the exam tomorrow! I would have had this up sooner but only discovered it today! His conversational tutoring style is a lot less filled with "um's" and other fillers which makes the video much easier to follow. Sometimes they're even shorter than Khan's so that he's not stretching to artificially fill up some required ten-minute benchmark.
This could help make or break some of the problems you'll face on the exam I would spend a little time searching through his topics to beef up on areas with which you're not so comfortable. This isn't nearly as cute or entertaining as Minute Physics, but the audiences are really different crowds.
That said, click over the links and this may help guide your learning this evening. Don't stress out!

+Joseph Meany


http://www.ted.com/talks/tyler_dewitt_hey_science_teachers_make_it_fun.html
http://dollhouse.wikia.com/wiki/Adelle_DeWitt
https://www.youtube.com/user/tdewitt451?feature=watch
https://www.youtube.com/user/minutephysics