The Chemportal

Rummaging through some old favorites, I found some some sites that I had employed during my undergraduate years which were….interesting. Here are two….

Tanabe-Sugano diagrams via Java applets

An interactive program for assignments that require investigations into Tanabe-Sugano diagrams.

Chemlab at Dartmouth

This site actually includes tutorials on the techniques that are employed with various labware and instrumentation e.g. digital spectrometer and volumetric flasks!

I’ve picked this problem from some general chemistry files that were retrieved from some tutoring sessions during my undergraduate years in chemistry (where I was the tutor).  Let me know if there’s anything erroneous in the content.

When a mixture of xenon and flourine is sealed in a glass bulb and placed in the sunlight, beautiful crystals of XeF2 are slowly formed and deposited on the walls of the container. (XeF2 is a volatile solid with a vapor pressure of 4.5 torr at 25 degrees C).

In one such experiment, a 10.0 L glass bulb is filled with 1.00 atm Xe and 0.100 atm F2 at 25 degrees C. After sitting in the sunlight for a period of time, 4.60 g of SOLID XeF2 is formed. The bulb is then removed from the light and the reaction stops. Determine the partial pressure of each gas in the bulb at this point in the reaction.

Since XeF2 solid was formed, the container is saturated with XeF2 gas.  The quantity of Xe and F2 which together formed XeF2 (g) can be ascertained by considering how much of XeF2 (g) as well as XeF2 (s) was produced.

Due to saturation, the vapor pressure of XeF2 is 4.5 torr, to find the number of moles of XeF2 gas that exists, the vapor pressure value is incorporated into the ideal gas equation.

4.5 torr XeF2(1 atm/760 torr)=0.0059211 atm XeF2

n=PV/(RT)=0.0059211 atm XeF2(10.0 L)/(0.08206 Latm/molK(298 K))= 0.0024213 moles XeF2

The problem states the amount of XeF2 that was formed as a solid, this amount is converted to the mole unit. 

4.60 g XeF2(1 mole XeF2/(131 g + 2(19 g))=0.027219 moles XeF2 solid

The total number of moles of XeF2 that was formed as a gas and solid is thus,

.0024213 + 0.027219 = 0.029640 moles XeF2 has formed

This means that we need to subtract this amount from the initial mole values for Xe and F2.  The stoichiometric equation, Xe (g) + F2 (g) —-> XeF2 (g), indicates that the ratio between the reagents and products are unity; the number of Xe (g) and F2 (g) are equivalent with the number quantity of XeF2 (g) that is subsequently produced.

Moles of Xe (g) consumed = Moles of F2 (g) consumed = Moles of XeF2 (g) and XeF2 (s) 

The amount is 10 times greater for Xe since its initial vapor pressure is 10 times higher

1.00 atm/0.100 atm = 10, 0.40893 moles Xe

0.40893 initial moles Xe - 0.029640 Xe reacted = 0.37929 moles Xe remain
0.040893 initial moles F2 - 0.029640 F2 reacted = 0.011253 moles F2 remain

Incorporate these values into the ideal gas equation to calculate the pressure value.

P=nRT/V=0.37929 moles Xe(0.08206 Latm/molK)298 K/10.0 L=0.92751 atm Xe

0.0059211 atm is the vapor pressure for XeF2 as was stated already at the introduction.

Edited 02/27/2007 for simplification.

I had to report at work today by 5:00 A.M. due to a validation protocol that is being implemented over the next two weeks.  First I didn’t recharge my phone, then I didn’t bring my electronic key, and I was low on gas……..the latter would have been problematic since no gas stations are open at 4:00 A.M. in the morning.  However, a Quick Trip gas station was open (“QT”), in fact, it was basically the only place that was in business at such a time. 

I saw seven other cars on my way to work, one of them was a police car which was right in the middle of the road, apparently the cop was taking care of business with two other cars; perhaps they got caught dui.  He eventually noticed that the traffic was building (the four other cars I witnessed during the whole trip to work) and made amends to direct the traffic around the two cars to which he was attending to.

I arrived at the work site to find that I had not brought my electronic key to access the building, the battery was quite low on my phone,  I was hoping that an anvil would drop from the sky, knock me unconscious, put me out of my misery.  Fortunately, I was able to make a single phone call to have one of my co-workers open the door from the inside.

Blog.com is currently having some bug problems with their blog layout feature, it’s been a couple of weeks now and thus it seems that they have other priorities.  ‘Chemportal.blog.com’ may become ‘Chemportal.wordpress.com’ or ‘Chemportal.blogspot.com’ pretty soon.

 Ladies and Gentlemen, THE MAN…….E.J. Corey 

Today was pretty sobering for me, I spent most of the day alone at a park, taking pictures of migrating geese and people playing with their remote controlled sail boats.  Yep, it seems that the glory days of partying and a fast paced social lifestyle are pretty much over for me.  The pics shall be posted soon.  Yeah, I got a new camera by the way, a Kodak digital camera model C743.  It doesn’t actually look the the box and the ad on the web indicates

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=9571&pq-locale=en_US&_requestid=4025

it’s made out of cheap plastic, and the camera isn’t quite as appealing and shiny.  It’s endowed with pretty good technology however, and so I’m not gonna return it.

My day at the park, yeah, that arrow is pointing to one of the remote controlled sail boats, there were actually a few more of them, seems that a couple of guys were racing them around the lake coast.

Kyle at http://www.thechemblog.com has posted something interesting at

http://www.thechemblog.com/?p=386

And here’s my reply to his post in the comments section associated with this article of his.

——-

You’ve been quite productive, on a Saturday.

Yeah, some people are just smarter then others and possess a higher form of intellectual facets then others, for science in particular, spatial IQ is quite valuable and some are obviously very good at taking the exact 3D geometric representation of an object rotating it in their minds while others can see merely a vague structure without any concrete details. There’s also the notion of raw brain power, and this probably exists also. Yep, some people are just better endowed and pretty much have it very easy when it comes to success driven by their intellectual prowess and live a totally different existence. 

However, IQ tests are relevant strictly towards diagnosing retardation and the treatment thereof, getting a good score on a IQ test is going to get you into gifted programs; yet a lot of people in gifted programs have been put in to it by delusionally motivated parents. IQ is not a predictive measure of intelligence, it’s simply a criteria for admission into gifted programs. Intelligence can only be really measured by one criteria, and that’s the fruitfulness of one’s career, such as that of E.J. Corey, and Buckminster Fuller; he was in the same gifted program as that of William Sidis, as most of you probably know, the Sidis isolated himself from academia early despite reputed as having the highest IQ quotient ever.

By the way, this is totally going in my blog.

——-

Figure 1 Pic from nanoscience.com featuring the topographical image of a Langmuir-Blodgett film.  The top arrow points to regions that have been more or less destroyed relative to that associated with the shorter arrow at the bottom.

 Benjamin Franklin analyzing his experiment at the pond within Clapham Common

It was Irvine Langmuir in 1918 who discovered that the constituents of an amphipile monolayer substance can be transferred to a substrate and subsequently placed distinctively on a solid surface (Figure 2); a monolayer that lies above a major liquid influences its surface tension ( 72 mN/m for water, almost zero with a monolayer on top).  Langmuir’s assistant, Katherine Blodgett discovered 16 years later that the process could be repeated so as to result in a multi-monolayer stack of any desired thickness essentially making up what is now deemed as the Langmuir-Blodgett film (Figure 1). 

Figure 2 Solid polar substrate is immersed (or emmersed) into the solution to collect the organic monolayer.  More about the details of this phenomena can be found at http://www.ksvltd.com/content/index/keylbfilm .

Applied technology, BAM  http://www.nima.co.uk/basics/basindex.htm

“A monolayer is extremely thin, approximately ½% of the wavelength of visible light. The relative effect it has on the electric field reflected from a water surface is therefore very small and the monolayer is under normal conditions quite invisible. However if the water surface is illuminated with p-polarized light at the Brewster angle, there is no reflection from the water surface. The background is then completely dark and it is possible to make out the tiny effect of the monolayer. This is the principle of the Brewster angle microscope or BAM.  

The BAM was invented independently and almost simultaneously by two groups, that of Jacques Meunier in Paris, France and that of Dietmar Möbius in Göttingen, Germany.  For the first time it was possible to see exactly what a monolayer looked like, and to provide definitive answers to questions which had remained open for 50 years. For example the picture on the left shows the pattern of condensed domains surrounded by a matrix of expanded phase at the main phase transition of a lipid, proving unequivocally that it is a first order transition (Figure 3).”

Figure 3 BAM picture of liquid condensed phase in matrix of liquid expanded phase. DMPE - dimyristoyl phosphatidyl ethanol amine.  

“Modern technological interest in Langmuir-Blodgett (LB) films began with the work of Kuhn, based initially in Marburg, Germany in the late 1960’s[5] and later in Göttingen (where his group gave birth to Nima’s partner company NFT). Over a decade, Kuhn and his colleagues showed that LB films could be fabricated with all the characteristics required for an information-processing technology in which individual molecules perform distinct functions. They showed not only that the films could be made with molecular-scale patterning, but that previously deposited ’sub-assemblies’ could be manipulated to build up more complicated systems[6]. They showed that the built-up films could remain stable for long periods, and that their defect levels were acceptably low[7]. Kuhn’s exciting results and his effective communication of them not only around Europe but also around the world inspired many groups to carry on his research. ”

From http://www.nima.co.uk/basics/basics1.htm 

More relevance of these monolayers and technological applications (e.g. molecular electronics)…….

http://www.nima.co.uk/basics/basics4.htm

I just got an offer for an interview to become a QC Chemist at Barr Pharmaceutical however the position is located at Forest, Virginia.  Don’t quite know how nice Virginia is, however, the tasks involved with the position include operating some instruments such as HPLC, GC…….

• Perform instrumental analysis using HPLC, GC, UV/VIS, FTIR, and dissolution with robotics
• Ability to create and maintain lab record documentation (notebooks & computer-based)
• Perform algebraic calculations to quantify test results, computer analysis with chromatographic results for use in a LIMS
• Perform analysis and provide feedback on systems to promote continuous improvement
• Perform routine maintenance of lab equipment as needed

http://www.barrlabs.com

The training on such instrumentations would open a lot of doors in to what type of jobs I can fulfill in the future.  However, I currently live in Georgia and am a bit perplexed regarding why they would seek to hire an employee out of state instead of someone that resides in, let’s say, Virginia (Forest, Virginia that is)?

I’ve recently encoutered a physical chemistry problem which reminded me of just how messy a simple problem can become when it came to sorting out the units.  

The root mean square velocity of oxygen molecules is 480m/s while the pressure is 20kPa.

What is the concentration (particles/volume) of oxygen?

Sourced from

http://www.physicsforums.com/showthread.php?p=1216079#post1216079

The equations that were utilized to solve the problem can be found in the page that is hyperlinked to the above text.

The equation to plug in the numbers are pretty simple, however, one has to incorporate the right units for the gas constant, here are just some of them (Figure 1)……. the same goes for the value of k.

You won’t find problems like this anywhere in your undergraduate courses besides in Physical Chemistry.  Unless you’re of a different major.

(n/v)=20 kPa(1000 Pa/1 kPa)(1.3806503 × 10-23 m^2 kg s^-2 K^-1)3/[8.314472 m^3 · Pa · K^-1 · mol^-1(16 grams of Oxygen/mole of Oxygen)(1 mole/6.022 x 10^23 atoms)(1 kilogram/1000 grams)(2 atoms of Oxygen/1 diatomic molecule)(480 m/s)^2]= 0.00813782909722 moles/m^3

(0.00813782909722 moles Oxygen/L)(6.022×10^23 molecules Oxygen/mole)= 4.900600682 x 10^24 molecules/m^3

It can get substantially worse….I’m sure you grad students remember.

                                                    Figure 1 Gas constant values obtained

                                                   from Wikipedia 

                                                    http://en.wikipedia.org/wiki/Gas_constant  

I tutored at Kasamba.com and Expertbee.com during my undergraduate years for the purpose of acquiring supplementary income.  On any good month I could earn an extra $400.00, this was all after my ratings had gone up to a good extent so that my name appeared on the search results for “Chemistry” on the main page for Kasamba.com.  Tutoring usually consists of providing explanations via email or live chat.  The live chat mode was particularly useful, the client seeking help could actually witness the typing up of the explanation in real time.

The professionals on Kasamba.com are credible, however, none of them are verified (at least not to my knowledge).  The system with Expertbee is a bit different and a lot of their features are currently under development; Wayne, who hosts the site has been helpful all the time.  I’ve heared reports from my clients, however, that Kasamba.com has been pretty vicious and deceptive when it comes to charging their clients and their customer support department is almost nonexistent (with respect to the professionals who register as tutors their as well as towards client concerns).  I wouldn’t be surprised if someone got ripped off and didn’t get a response at all.  I’ve sent a couple of emails to them and at times didn’t even get an answer; which impressed upon me that they were utterly disrespectful.  The attitude seems to indicate that they could do business one way or another, they can address the concern of the consumer or not since the majority of us are ignorant on how to adequately prosecute such secretive institutions as Kasamba.  This type of a demeanor is rather disturbing to say the least and dispicable.

There is only a fax number and an email address for the contact page.  I’ve only had few problems with them so far, even though they take away 30 percent of the earnings from the session with the client.

If anyone has problems with the site, don’t go to the Better Business Bureau, better yet contact the Department of Labor and they should be able to assist in the matter or at least provide good references and other directional advice so that the issue at hand can be resolved.

It seems that most of the popular Chemistry blogs online these days relate to the organic synthesis field.  I’ve only been able to spot two P. Chem. blogs thus far

http://thedisgruntled.blogspot.com/

http://chemical-quantum-images.blogspot.com/

One apparent explanation for the lack of online Physical Chemistry blogs is because most “physical chemists” associate themselves more with the physics and math fields, some of them can be found in discussion boards which are compatible with Latex or which allow the use of other mathematical tools and hyped up posting mechanisms for quick tempered mathematicians and physicists.  Perhaps they don’t even have time to write a decent blog article.  Maybe Physical Chemistry isn’t considered “Chemistry” rather of “Math and Physics”.

I would personally enjoy seeing more chemistry blogs that have mathematical perspectives in its contents during the year of 2007 and perhaps some blogs that share enthusiasm in the learning of various general chemistry concepts. Discussions centered on unique features in derivations and real life applications can be good within a Physical Chemistry blog for instance. Discussions based on extended readings for general chemistry concepts can make any general chemistry blog an interesting read.

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