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A Chemistry Question, Daily

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January 24, 2010
13:11
Liquid Calcium Hoax
» ‎ A Chemistry Question, Daily

Hello guys! I bring good news to you. I am qualified for the National Level of the Romanian Chemistry Olympiad 2010, which will take place this year at Pitești, a nice city, where I've lived for almost half a year in 2004. I am quite happy about my results at the county phase, but I would like to believe this year will show up to be more rewarding than the previous one :D Unfortunately this year the Olympiad has no website, which is pretty annoying because we can't get any kind of updates about it. Although there is no way of directly receiving information about the Olympiad, my teacher has sent me the syllabus, which includes hydrocarbons (alkanes, alkenes, alkynes, polyenes and aromatic hydrocarbons), alcohols and just might include phenols, but that's not for sure.

And now, a little thing I've noticed on a Colgate® toothpaste tube:

On the back of the tube, it said: "contains liquid calcium". Well, chemically speaking, liquid calcium is obtained when you heat it to 842 °C in an environment lacking oxygen, because if oxygen would present self ignition of calcium would happen. So, clearly, this can't be the case admitting the last time I checked, I wasn't brushing my teeth with a molten hot red paste :))

Maybe they wanted to say "a liquid solution of CaF2", but again it has to be a very, very diluted one, judging that the solubility in water 20 °C is roughly 0.0016 g/100 mL. Therefore, even this more scientific formulation is quite improper, though this might not be just a minor mistake, but more like an eye catchy description for customers to buy it. Nevertheless, everything should have a scientific basis, which in this case lacks somehow. Hope I wasn't too harsh :D

Image from www.bigoo.ws
December 03, 2009
11:37
Fluorescein, a Pathway to Synthesis
» ‎ A Chemistry Question, Daily
Today, during a chemistry lab that I take at the local University (unfortunately lab sessions lack in our high school so I have to do and mend somehow), we were expected to synthesize the fluorescein. So, with excitement, we started to work. For the synthesis to take place, I used phtalic acid and resorcinol (or 1,3-benzenediol). As a catalyst it is recommended to use ZnCl2, but I used concentrate sulphuric acid (purity >99%) instead.

Substances needed: resorcinol, phtalic anhydride (or phtalic acid), zinc chloride, sodium hydroxide, water

Glassware needed: a crucible, a bunsen burner, 2 berzelius flasks, one pipette

Working technique
1. In a small crucible, a few grams of solid phtalic acid and an equal amount of resorcinol are added. Followingly, the crucible is put on the sand bath at around 200^o. After the mixture melts, it is left boiling for about 40 minutes.
2. The molten mixture is cooled for five to ten minutes and then moved to a berzelius flask. Now NaOH 10-20% is added. As a result fluorescein will be generated and the mixture will turn from dark brown to light green.
3. Using a pipette, take five millilitres of the green dye and dillute it to about 10%. A light green fluorescence phenomenon will be observed in dim light, or in UV light. And here is the result :D (image taken by myself)
Tips

Although this is the first time I synthesized this compound, from the experience of others, I can draw a few conclusions from this experiment:
- You can use, not only ZnCl2, but also CaCl2 as a catalyst.
- If you choose to work with highly pure sulphuric acid as a catalyst, as I did, be extremely cautious of the way you are handling the acid, because is highly corrosive, especially in these concentrations (98-99%)
- Instead of phtalic acid, phtalic anhydride works as well. The reason for this, is that at these temperatures (~200^oC) the acid is obliged to eliminate water, so anhydride is formed, that further reacts with resorcinol.
- And the most important, have fun :p
Applications
"Fluorescein sodium is used extensively as a diagnostic tool in the field of ophthalmology and optometry, where topical fluorescein is used in the diagnosis of corneal abrasions, corneal ulcers and herpetic corneal infections. It is also used in rigid gas permeable contact lens fitting to evaluate the tear layer under the lens." - excerpt from Wikipedia One of its less common uses is the annual festival of St. Patrick's Day, when the Chicago River's waters are dyed green. Image from Wikipedia And now, as an ending, a couple of other images concerning the experiment today:
November 16, 2009
11:54
ChimeXpert International Competition Begins Today
» ‎ A Chemistry Question, Daily

The first phase of ChimeXpert International Chemistry Competiton has started today. This phase consists in a set of three tests on the internet, for those of you who have already registered and paid the registration fee of 40 RON (12 euro). All three tests are multiple choice type, with 40 questions. The solution for the first test can be submitted on their site until the 28^th of this month (November).

All competitors who fill in all three tests will go to the regional phase where the real selection will take place. The marks at these three tests are used for selecting the contestants that will go further to the International phase in case of equality between the first scores at the regional phase.

Good Luck!
November 11, 2009
12:31
The mistery of the water droplet
» ‎ A Chemistry Question, Daily
Yesterday, as I was in the chemistry lab, working at an addition reaction to an alkene, I needed to use a bunsen burner, for the preparation of the proper alkene. As one of the rubber tubes was leaking, I took a roll of aluminium foil in order to wrap some around the portion of the tube with the little hole in it. Accidentaly, I dropped the foil directly above the flame. It immediately turned red hot. And because I had my hands wet, a droplet of water fell on the aluminium foil. Then, a very strange thing happened. Instead of vapourising instantaneously, the droplet persisted on the foil for about 15 seconds. Judging that the aluminium foil turns red at temperatures clearly higher than 100^o C, the water drop was expected to vapourize in a far smaller period of time. Moreover, the water drop became rather spherical, as it seemed to have fallen on a hydrophobic surface. At a first glance, I thought that it was just something unusual and that at another try the tiny water drop would evaporate immediately. So I repeated the experiment three or four times. Each and every time the results were the same. Even more, When I maxed the heat from the bunsen burner, the droplet persisted more on the foil. It was absolutelly unbelievable. Now I had a problem. An explanation of the phenomenon surely existed, but it was somewhere lost in the mist and I couldn't see it at all. A couple of scenarios crossed my mind, but both proved to be wrong:
1. Maybe the aluminium in the foil turned by burning into Al2O3 that had a different thermal conductivity, and therefore, water droplets could withstand heat for a longer period of time, beacuse aluminium oxide transfered heat more slowly. But then, why did the droplet have almost sheprical shape? I mean, aluminiunm oxide is not a hydrophobic substance.
2. But what if the vaporisation process occured only where the water layer was thinnest? This meant that vaporisation could've given the droplet a spherical shape. But here lays another impediment. If vaporisation occured so fast, the droplet would have dissapeared instantaneously. So this is not the case!
As I had no other ideas, I posted the question on ChemicalForums.com. Thankfully, someone reminded me that this is due to the so called, Leidenfrost effect. "The Leidenfrost effect is a phenomenon in which a liquid, in near contact with a mass significantly hotter than the liquid's boiling point, produces an insulating vapor layer which keeps that liquid from boiling rapidly" - extract from Wikipedia. Image: Wikipedia In addition, the bigger the difference between the tempreratures of the two bodies, the harder does the droplet vaporise. Why? Beacuse the vapour layer under the drop is thicker, so it provides a better insulation. The vapour layer under the droplet litteraly makes the water particle float. This causes the particle to become almost spherical. So for now, I really know what happened there. I think this very interesting subject, that echoed through my head in the last two days, is worth studying in more detail with another occasion. See you next time!
October 18, 2009
10:10
No Sweet Sense for Sweet Cats
» ‎ A Chemistry Question, Daily

We all like to eat sweet desserts; ice cream, candies, cakes, they're all part of our lives. The sweet taste is an ubiquitous element in all kinds of diets. And we, humans, are not the only lovers of sweet. Species from the Canidae family like the dog and its relatives also have an avidity for sweet foods, sweet being the indicator for carbohydrate rich edible things. Also, members of the Equidae (the horse and the donkey), Suidae (the pig), Ursidae (the brown bear - Ursus Arctos) amd other omnivourous species have the same tendency towards sugar.

However, not all animals are capable to sense sweet. Somehow, in the evolution process, a specific family of animals have lost this ability. It's the Felidae family. Little is known about the so called "big cats", such as the lion, the tiger or the panter. What is certain, is that the common cat (Felis Catus) is unable to detect the taste of even the most flavoured of sweets. It has been discovered that a deletion of an exon (coding part of the DNA) in the TAS1r2 gene is responsible for the loss of sweet taste in cats.
The deletion is marked in red. The numbers between brackets represent the exact number of nucleotides in each exon (the picture is adapted by me from the figure 2 of this article which I used as main reference).
Evolutionists say that natural selection didn't allow this taste to exist in cats because there was no need of it. The members of Felidae family are entirely carnivorous. The sweet taste allows omnivorous creatures to tell the difference between rich and poor carbohydrate food. But, because of the fact that meat of any kind is highly rich in these nutrients, there is no need for such a sense in cats. As a result, a mutation took place in this gene, taking out the unnecessary code, at a certain moment in the past.
Our cat on the fridge :-)
However, this certain moment is compuslorily subsequent to the swarving of cats from dogs, by reason of dogs manifesting a strong likelyhood for sweet. Personally, I think that humans may also have enhanced the dogs sweet sense as a result of the domestication process (so that the dogs have become almost omnivorous), but meanwhile, I'm sure that the contribution brought by humans in the development of canine taste senses is irelevantly small to be taken in consideration.

I would have also wanted to talk about a fellow gene of TAS1r2, the TAS2R38 gene (responsible for the ability or disability to taste PTC - a horrendously bitter chemical substance), but considering the length of the post, I'll do it with an other occasion (until then I would recommend you this wonderful book I'm reading: "When a Gene Makes You Smell Like a Fish"). See ya!
October 13, 2009
12:22
What Element Would You Like for Birthday?
» ‎ A Chemistry Question, Daily

Today is quite of a special day, my blog turns one :D For making this day like so, I made an appraisement on 50 people, regarding the topic "What element would you like for your birthday>".

Besides naming an element I expected also a reason for choosing a certain element. Almost a third of the participants answered Oxygen, because it is crucial for life developement on Earth. On the second position was Hydrogen due to the fact that in combination with the element mentioned earlier forms water. With only four votes, Carbon is on the third position, as consequence for its ability to form an infinite number of organic compounds.

People also had spontaneous reactions some of which were very funny. As an example, one russian guy said Chromium because it is used for plating guns (a pretty weird answer). Others said that gold or silver would be the perfect options just because they are shiny. Last but not least, a woman let me know that she desires an element that she could put in her husbands food so that he would stop cheating her in love :)).

Personally, I would choose Manganese, as it has different colours from one state of oxidation to an other (Mn⁷⁺ is purple,2Mn⁶⁺ is green, Mn⁵⁺ is cold blue and Mn²⁺ is crimson red).

I hope you like today's post. See you next time!
September 30, 2009
13:18
Olynth Nasal Spray
» ‎ A Chemistry Question, Daily
I have recently caught a cold. In the first days, apart from the sore throat sensation, my nose was totally congested, so I had to use a nasal spray. My option was Olynth. From curiosity at first, I read the list of components of this medicine. Then I thought I could find the way each and every of them acts to produce the general decongestioning effect of the spray and the way they are synthesized.

The composition of Olynth was: xylomethazoline chlorohydrate (the active substance), sorbitol (actually 1,2,3,4,5,6-hexanhexol), monosodium phosphate, benzalkonium chloride and disodium edetate.

The roles were the following:
- Xylometazoline can stimulate adrenaline receptors. As a response, the organism will consider the stimulus to be actually adrenaline and capillary vessels of blood will constrict (vasoconstriction is one of adrenaline symptoms), not allowing blood to irrigate the area. The capillary vessels near the mucus secretion glands will not be activated, so the process of mucus secretion will stop. As a remark, due to the adrenaline mimetism capabilities, xylometazoline is not recommended for persons with heart diseases.
- Sorbitol and the phosphate have the ability of retaining water (phosphate is a hidrate)
- Benzalkonium chloride acts as an antiseptic. The disodium edetate is a preservative, useful for enhancing the action of benzalkonium chloride.
Synthesis
Xylometazoline has a pretty easy way of synthesizing, albeit it is not visible from the beginning if we are to propose a possible method for doing this. So, after trying to find by ourselves the synthesis, Otilia, Silvian and I, finally bumped into the method sketched in this book: Strategies for Organic Drug Synthesis and Design.
The benzalkonium chloride is produced by reacting N,N-dimethylbenzylamine hidrochloride with a haloalcane. The reaction occurs as following:
The next reaction, although not very difficult to understand, it intrigued me because NAD⁺ and NADH, present here in the synthesis of sorbitol, have too a major role in the glycolisis process. NAD⁺ is a substance made of ADP and a ribose (pentose).
For the symplification of the synthesis of sorbitol, I'll show only the part of the molecule implied in the reaction. As it can be seen, when NAD⁺ reacts with D-fructose, NADH and sorbitol are produced.
I'll end this post by showing the structure of disodium edetate and monosodium phosphate.
Disodium edetate Monosodium phosphate So next time you'll use Olynth, you will definitely know how it actually works and how it's made. See you next time!
September 25, 2009
10:37
My Summer Holiday - Bicaz Trip
» ‎ A Chemistry Question, Daily

On the 26^th of July, me and my family started our family trip. We stayed at a floating hotel on the Bicaz Lake. The accommodation was pretty nice, and we had a great view of the lake from that point.

In the first three or four days we stayed at the hotel on the roof, getting a nice brown tan and also reading on chaise longues. Actually from this point of view, these eight days at Bicaz were really fulfilling: I have read Six Easy Pieces (R. Feynman), The Blind Watchmaker and A River Out Of Eden: A Darwinian View of Life, two books about evolution and natural selection from a very interesting perspective by the same author, Richard Dawkins.
In the fourth day, we went in a small trip around Bicaz Gorges and the Red Lake. When entering the Bicaz Canyon, the road becomes suddenly very tight. Rocky, vertical walls rise from both sides of the road and the Bicaz brook is on the right. It is extraordinary too see what such a small creek could have dug in millions and millions of years.

The Red Lake, a natural dam river, shaped in the form of an L, attracts many tourists, including us. A footpath surrounding the area is a great place to spend one or two hours walking. What is unique about this lake, is that pine stumps rise from the shallow water. Also, protected plants can be seen here on the edge of the track. For instance an endemic species of flowers, found only in Romania, Dianthus Callizonus, can be easily spotted here:
Dianthus Callizonus - endemic species of plants The Red Lake
As the fifth day came, we put on our sports shoes and reached the summit of Ceahlau mountain (Toaca Peak, 1907 m above sea level). It was a one hour hike from the base to a chalet at 1220 m high where we stayed and watched the scenic views and then went on climbing for another 2 hours and a half. Mainly, the track had a very steep angle but there were also plain bits of the footpath.
Me and my mom not being aware of the dozen kilometers path we were desiring to follow 'till the end of the day :D
We walked along the route for about an hour and a half until we found some benches to sit on. The place had a very spooky name "At the graves", but anyway we stopped to take a little rest.
Nothing to say, just watch
After another half an hour of hiking we stopped again (lazy us) at a place called "Cusma Dorobantului" (the soldier and his weapon), name inspired by the following piece of rock cutting through the sky.
Me on a pile of rocks
When seeing that the track leads us to a pasture, we were kind of relieved because we realized that this was the end, the so much desired peak. Although a splendid view was opening in front of our eyes, we made an idea of how much we still had to hike.
See that rocky peak? There we had to go
And as usually, when we finally were on the peak, the camera's battery died :)) . So sorry folks, but no images from the Toaca Peak today.

I leave the best subject for the next post: A Bulgarian All-Inclusive Experience.
NOTE: This post belongs to the series of posts "My Summer Holiday". The other post in this series is My Summer Holiday - The Olympiad.
September 24, 2009
9:43
Organic Chemistry Calculator
» ‎ A Chemistry Question, Daily

It's been a while since I last used a free online tool for chemistry, that combines different aspects of organic chemistry, such as: structure, stoichiometry and general reaction mechanisms. But yesterday evening, while searching on the internet, I found a seemingly useful, free, online tool that definitely caught my eye straightway.

It was a quite complex software produced by professor Andreas Herrmann's team in the Polymer Chemistry and Bioengineering department at Groningen University. The software allows you to draw the structures of different compounds and put them in printable version, to calculate the ammounts of substance needed in different organic reaction processes containing up to six reactions. So, I consider it to be pretty useful. Its link is the following: [chemist.hosting.paran.com]

To test the efficiency of this software, let's try to synthesize an organic compound, for instance urea (the first organic compound to be ever synthesized), from inorganic compounds. Firstly, fill in the name of the reaction in the title section, in this case Wöhler Synthesis. In the structure drawing section, let's draw the structural formula of urea.

Click on the double bond tool and then click in the middle of the drawing field.

Select the Oxygen tool and click in one of the double bond's ends.

Now select the simple bond tool and double click on the other end of the double bond. By doing this, two simple bonds will appear connected to the double bond.

Select Nitrogen tool and click on each of the simple bonds' free end. Now, urea should look like this:

Now look at the proper calculator. You know that AgNCO + NH4Cl → (NH2)2CO + AgCl is the reaction implied. In the starting formula cell, introduce the formula of AgNCO and in the product formula cell write the formula of urea ((NH2)2CO). By pressing the ">" sign near these two cells the molar masses will be automatically generated. As a starting amount of AGNCO let's take 100 grams, for example. After doing this, press again the ">" in the current cell. The number of moles will be generated this time. Because the equation is balanced with no coefficient, we leave the equivalent section untouched (the default value is 1). Now we can calculate the amount of urea produced by pressing "evaluate". If the result is 40.069389 then you have understood how to use this organic chemistry calculator. If not, re-read the tutorial and do exactly as told because I consider this tool very interesting and useful.
September 23, 2009
7:15
ChimeXpert International Chemistry Contest
» ‎ A Chemistry Question, Daily

Hi there again! A few days ago, as I was talking to one of my friends, Victor (he also went to the same chemistry contests as me) on Yahoo Messenger, I realised that the registration phase for ChimeXpert International Contest has recently begun.

Chimexpert is an International Chemistry Contest, organised by Romania and hosted by Satu Mare every year. Up until now, students only from Romania, Italy and Hungary have participated, but this year the organisers intend to bring contestants from other countries too, so all and sundry is welcome.

In order to register for the contest you must first fill in an application form online and then pay a 12 euro tax (or 40 RON). You can find more information at the Regulation section, on their website.

About my personal experience with this contest, I can tell you that last year I participated at the International phase and returned home with a III^rd prize (as a result, after the proper competition I made a post about it). It isn't bad my result there, but I definetely know that I could have done better. Hope to see you there at this year's edition!
August 27, 2009
4:20
My Summer Holiday - The Olympiad
» ‎ A Chemistry Question, Daily
It's a while since you last heard from me so let me tell you what I've done all summer long. To start from the beginning, I spent the first half of my holidays at home preparing for the Romanian National Earth Science Olympiad, then I went to the olympiad itself where I did pretty much nothing (but still gained some experience for the next years) and only then can I say that the proper holydays began (one week at Bicaz lake and two weeks in Bulgaria).
Brain Fitness - preparing for the Olympiad
Our holydays began this year on the 15^th of June, as usual. Due to the fact that I was qualified for the national phase of the earth science olympiad, I started my preparation from day one. The contest itself covered 4 major areas of science: geography, physics, chemistry and biology. For each of these disciplines, I had some reference books reccomended by my teachers Lidia Minza (chemistry), Dana Samoila (biology), Ion Cioroiu (geography) and Doru Costache (physics):
- For biology, I have read some chapters focusing on ecosystems, biotope, biocenosis, food chains and more subjects like these, from an ecology textbook.
- The physics covered only mechanics which is good, because it was my object of study at the physics class this year. The recommended book here were "Fundamentals of Physics, Volume 1" (Halliday, Resnick, Walker) and "College Physics" (Sears, Zemansky, Young).
- Geography was a little bit trickier beacuse it implied a multitude of smaller domains such as climatology, hydrology, tectonic plate movement and a little bit of economic geography. Here, the reference books consisted in about 6 texbooks and one pretty old general meteorology course (Stoica, Cristea) for the first year students.
- As for chemistry, the knowledge of basic inorganic chemistry would have done the job.
I know these domains of study do not seem to have many things in common, but it was our job to find connections between them because we had to analyse a problem from multiple views.
The Olympiad
The olympiad took place in Urziceni, a little town in the southern part of Romania. A funny thing about its history is that in the Middle Age it was called "Vai de ei" (translated into english as "Poor them" - well, it seems it is still the case today). So, on the 19^th of July, knowing that we will spend one week counting the hours until returning home, because of boredom (or at least this was what we thought), we packed our luggage and left home. When we arrived, we realised that our accomodation place was a high-school campus almost in the middle of the field, at about an hour away on foot from the town through the crops!... We had a catering room (the food was pretty good), dorms with 6 beds each (for boys and for girls separately), shared bathroom and showers (for both boys and girls - actually this was not bad at all :)) ). To sum up, the accomodation was pretty good with one exception:
A very "cute" cockroach fellow in our bathroom :)) The exams were really tough, combining geography, physics, chemistry and biology and it was very hard to analyse one problem from all perspectives. At the theoretical exam the highest mark was sadly only 63 out of 100. For the practical exam, the organizers took us on a trip to seven different landmarks, in order to observe the chemical and physical processes in each and every of these:
1. the water filtering station (the filtering processes by physical and chemical means should have been observed)
2. the waterworks (here we should have kept our eyes on the purification process of underground water extracted from a 35 meters well)
3. the landfill (we should have compared and contrasted the ideal ecological landfill and the current situation of the dump site)
4. a natural gas compressor (here the chemical composition of the gas and the proper physical processing was the entire point of the visit - no photos here because we were put to sign a paper stating that the information unveiled here would remain confidential)
5. a dam over Ialomita river (the dam's functioning system was emphasized)
6. a bridge over the same river (erosion process highlighted here)
7. a field near Urziceni (we should have noticed the subsidence phenomenon happening)
So, from all the conclusions we had to make observing these places, we were given the practical exam. The subjects were not necesarilly difficult, but the lack of time was the major problem. We had about 7 subjects to solve in only 2 hours (and the solution for every subject was about two A4 pages long, so it was indeed a lot). After the exams, because it was very hot inside, we just took out all our matresses outside, in the schools courtyard, and staid awake till about 1:00 AM and only then, eventualy fallen asleep.
A poor quality photo (I'm the guy in green) - just wanted to show you the way we slept that night
But if you consider the life here to be peacefully and quiet, you haven't got the point yet. One night, as it was getting very late (about 1:00 AM) we went on the wrong street when returning home. Suddently, we realised that our route wasn't the good one, but too late, we all forgot the way of coming back. As it was not a good hour for knocking at people doors, we followed our intuition and went directly though the middle of a cornfield to the point where we thought our accomodation place was. After passing a railway line, a group of three weird looking, seemingly dangerous people came out of no-where. They started putting questions about where we were going, for what reason and things like that. Of course, being damn scared (we were only three boys and about four or five girls) we did not respond to them. Seeing no response from us, they started embracing the girls and trying to kiss them, knowing that we were defenseless. After a while they got bored seeing absolutely no reaction from us and left. With them going away from us, we were not only relieved, but we realised what could have happened in the worst scenario. Shall I be again in the similar conditions, I can tell you that I won't do the same thing again, that's for sure. I think you were used with photos from different moments, I know that, but I don't believe this was the right moment for a group picture, eh? :D

In the end, I came the 62^nd out of 85 (shame on me), but I think this year will count as experience for further contests and olympiads of this type.

Because the are so many things still to tell, I'll make two posts, one for each of other the two trips. So, coming soon... Bicaz Lake Trip and later, an All-Inclusive Bulgarian experience. :))
May 28, 2009
13:52
Petru Poni National Chemistry Competition
» ‎ A Chemistry Question, Daily
Last weekend, I went to the national phase of a regional chemistry contest, named after the Romanian chemist Petru Poni. It took place at Onesti, a town near one of Carpathians' mountainous areas. We arrived there Friday morning and came back to Galati Sunday evening.

The contest consisted in a theoretical exam and a practical part, at which I scored 94 respectively 73 out of 100. In the end I won a Mention which is pretty good, though I could have done a lot better.

After the contest we enjoyed a walk in the mountains, we hiked along foot-trails and we saw some beautiful sights. Although it was a rather short trip, we liked it - a little escape from school ;-)

The team of my county on the top of a hill during the walk, I'm kneeling in the middle

To sum up my first high-school year, here are my chemistry results in competitions, so far:
- 43rd edition of the Romanian National Chemistry Olympiad, 1-8 February 2009, Arad - Honorable Mention
- 5th edition of the ChimeXpert International Chemistry Competition, 27-29 March 2009, Satu Mare - IIIrd Prize
- 7the edition of the Petru Poni National Chemistry Competition, 24 May 2009, Onesti - Mention
I hope the summer will bring both fun and better preparation for the next year chemistry competitions.
April 16, 2009
7:17
A redox reaction in ChemLab
» ‎ A Chemistry Question, Daily
A chemistry laboratory isn't accessible to everyone, everytime, so I often use a virtual laboratory: Model ChemLab software (I have just an evaluation version and would be nice to receive some day a full/standard version). It's a pitty to find so few tutorials or resources on this product on the internet, so even the smallest contribution on the argument, counts. That's why my thought was to show some experiments made using this software. Let's compare a typical redox reaction (between KI, H2SO4 and oxygen) in the real lab vs. the virtual lab
In the real lab
The unbalanced reaction is:
KI + O2 + H2SO4 → I2 + K2SO4 + H2O

The installation for making this reaction in the lab

In the Florence Flask we have KI solution. In one of the two tubes that enter the flask through the cork is pumped continously oxygen (or at least air), and from the other is carefully dripped out sulphuric acid. When a dark violet-blue precipitate is observed on the bottom of the flask, the acid stream should be stopped. Immediately after that, the solution will turn dark blue because of the solubilisation of I2 in the liquid.
In ChemLab
After launching ChemLab, from the ChemLab Simulation Modules dialog, go to the Lab Wizards tab and choose ChemLab Wizard v1.7 (I run ChemLab v2.5 for Windows)

A reaction wizard will appear. Click Next.

Now complete the blanks with the Title, the Description of the reaction and the Author (your name). Then click Next.

The following step is to write the paths to the Introduction, the Procedure and the Observations files. Leave this blank, because it will help you only if somebody else will follow the instructions of the lab simulation you made. Only to mention. these three parts must be in ".RTF" or ".TXT" formats. So, click Next.
Select from the second list (Chemical Database) O2, KI H2SO4, I2, H2O, the K⁺ cation and the SO4^- anion and add them to the Added Chemicals list.
Select Potassium cation (K⁺) item in the first list and press Chemical Properties button. A dialog (Chemical properties:- Potassium Cation) will appar. Here you must follow a few steps:
- Uncheck Stock Chemical, as you don't want to have potassium from the early beginning
- Check Reaction Product checkbox
- Check Flame Test Color, as you will recognize, using a burning droplet of solution, the potassium cation by it's pink-red flame colour.
- From the color list, select the "Other" item:
- A dialog (Color) will appear. Select the pink-red color and click OK
- In the Chemical properties:- Potassium Cation dialog box, click OK
For SO4^2- anion, I2 and water, uncheck Stock Chemical and check Reaction Product.
For KI, check Solution and in the Molarity field write down 10M, because this is the molarity of the KI solution (pretty concentrated). As for the Flame Test Colour field, select that pink-red colour as earlier.
The same for sulphuric acid, but this time no Flame Test Colour.
Now, there is a little thing you must observe: ChemLab works only with liquids and solids, when talking about reactions. So, although it is practically impossible to dissolve oxygen in water, if we want to work with it, we will be forced to consider oxygen a solution (techlnically it would be possible if we cool enough the gas in order to make it a liquid - but this isn't our case).
All substances being added to the list, press Next.
It's reaction editing time! In order to do that, we first balance the equation by the redox method.
KI + O2 + H2SO4 → I2 + K2SO4 + H2O
O2^o --(+4e^-)→ 2O^-2....2.....1 2I^-1 --(-2e^-)→ I2^o........4.....2
So the balanced reaction is:
4KI + O2 + 2H2SO4 → 2I2 + 2K2SO4 + 2H2O
Now, that the reaction is balanced, we can start editing the reaction in ChemLab. Right-click on the Reactions node in the Reaction tree and press Add New Reaction.
A dialog will apear. In the Reaction Name field, fill in a name (for example, REDOX), then click OK.
Now, your window should look like this:

Drag one by one the substances from the right list to the left one. The Oxigen, the KI and the acid shall be the reactants and the rest of the substances should be the products.
When you add a substance to reactants/products another dialog is opened, asking about the coefficient of the substance in the reaction and a few other details. For example, for Oxygen put the coefficient 1 and click OK. For KI put 4, for the acid 2, for the potassium cation 4, for the sulphate anion 2, for the water 2 and for iodine it is 2. But when you are adding iodine, also check "In Solution", "Causes Colour Change In Solution" and "Uses Colour range". Don't forget to write down the minimum (0) and maximum (100) concentrations in the Low, respectivelly High fields. Select the blue colour from both two lists.

Now, that all substances have been added, your window should look like this. If so, click Next.

In the lab options window that you are facing now, check Include Metal Wire.

The next frame shows us an Add Indicator option; but because we don't need that now, we will just click Next.
The next frame shows a molecule viewer option. Skip it if you don't have molecular models for these substances.

The wizard is finally ready. All you need to do is to click Finish.
Now don't panic. After clicking Finish, it will show you 3 errors. On each and every of them click OK (these errors are caused by the absence of lab documentation files that we don't need for this demo).

Now we can start the simulation.
1. Take a 100 ml beaker (by right-clicking and then selecting Beaker, respectivelly 100 ml Beaker).
  And here it is our Beaker.
2. Fill it half with acid (50 ml)
  - Right-click and select Chemicals
  - A dialog box will appear. Select the sulphuric acid and as a quantity, type 50 ml.
  - The half-full beaker will look like this:
3. Fill an other beaker 1/4 with liquid oxigen (25 ml).
4. And an other one with KI (25 ml).
5. Take a big 250 ml Beaker and pour in it first the oxigen, second the acid, and third the KI solution (you can pour a substance into a vessel by placing the substance that will be poured above the vessel, right-clicking on the first container (that will be emptied) and selecting Pour/Decant).
6. After pouring the KI solution, the mixture should go dark-blue.
Sorry for the length of this post, but I wanted to pass through every step in order to make the entire virtual experiment clear. I'll also try, if you liked this, to make different experiments and describe them in ChemLab.
April 05, 2009
12:32
Bloody Chemistry
» ‎ A Chemistry Question, Daily
As I was at Satu Mare, in the middle of the poster session, I saw a poster with a very interesting topic: fake blood, an application of chemistry in cinematography. When I returned home, I've made a little bit of research on the subject and here it is.
The fake blood effect
Fake blood is widely used in action films, thrillers, horror films and westerns. There are many ways to prepare fake blood but only one of them truly gives the impression of real blood.
Hope you aren't scared of that guy up there :)) It's just K3[Fe(SCN)6], you know!
April 03, 2009
8:34
Excessive water drinking really makes people fat?
» ‎ A Chemistry Question, Daily
Some of you may have known that excessive water drinking makes you fat. Well, nutritionists and anatomists have been (and still are) in a continuous dispute on this topic. Personally, I consider this subject to be very interesting, because at a first glance the subject seems paradoxical.

What do nutritionists say?
Technically, water has no calories, so you can't deposit any of it's energy because it hasn't any (I remind you that this is energy from the burning of the nutrients). Its only use in the organism is that of being a very good transportation environment in the form of plasma in blood (blood plasma is more than 90% water):
- It won't react with any of the nutrients that the organism needs
- It is a polar substance that can dissolve all polar compounds and can transport as a suspension the apolar ones that won't normally dissolve in it.
So there would be theoretically no chance for you to get fat. Even more, if you drink cold icy water at 0^oC, your body has to warm it before putting it in the circulatory system. So 100g of water will consume 2 Cal, which means that it will even make you thinner (of course somewhere around zero point zero and a little bit grams, but hey it's weight loss wright? :)) )

What do anatomists say?
Except of the fact that water makes us gain weight simply by the weight of the water itself, there is a more profound explanation to be found at a much smaller scale, the cell level.
It is known that a cell's membrane is a phospholipidic three layered tissue which is composed from membranous units. A unit has both a hydrophobic and a hydorphilic head. This maintains a constant concentration in water of the cytosol between 60-70% as far as I can remember from biology classes. When the concentration in water of the cell belittle under these values, some proteic tubes are opened in order to let the water in. The same happens when the difference between the outside and the inside is pretty significant (the outside is richer in water in this case).

If a person drinks a lot of water regularly, the blood plasma will be always very rich in water, so cells will receive continuously water, until the interior concentration will equal the exterior concentration. Like a rubber gum, if maintained elongated for a long time, the cell membrane will lose its elasticity and suffer plastic deformation. From this point, the cell membrane can't regain its initial shape and will occupy a larger volume. That's the story for a single cell. But when the measuring unit is several billion cells ( around the number of the cells in the human body) they will have a considerably bigger volume, and will give the impression of a fat person.
So, next time don't put the blame on hamburgers for all the fat. Blame water :)) !
April 01, 2009
7:08
ChimeXpert International Contest
» ‎ A Chemistry Question, Daily

Last weekend I participated at the 5th edition of the ChimeXpert International Chemistry Competition, which took place this year at Satu Mare. Even though I've obtained a III^rd prize, I am pretty disappointed with this result because I was really close to the second prize. The competition itself consisted in two parts: a three hour written test and a poster presentation in no more than three minutes. I chose the carbon nanotubes as topic for my poster, a fascinating subject that I have researched browsing these books as much as my understanding level allowed me: "Understanding Carbon Nanotubes: From Basics to Applications" (an advanced book, but full of applications; this book helped me to form a practical perspective on the argument), "Science of Fullerenes and Carbon Nanotubes: Their Properties and Applications" (it talks a little about nanotubes but describes very well their special properties) and "Handbook of Carbon, Graphite, Diamonds and Fullerenes: Processing, Properties and Applications" (it helped me figure out how carbon nanotubes are produced).And now, some photos from the competition:
Me coming through the hallway
All seven of us from Galati county at the official opening of the competition (in the third row)

Hungarian folk dance was a nice show after the opening ;)
The classroom where I sit the written test (I am in a white shirt in the back of the photo)

Me and my poster

After the competion, in our hostel-like room
After two days of competition, 1000 km from home, we returned to Galati. It was pretty nice that everybody from our county returned with a prize, whereas contestants from other counties returned home empty-handed. Lucky us!
February 17, 2009
11:38
Romanian National Chemistry Olympiad and ChimeXpert
» ‎ A Chemistry Question, Daily

Hi! In the last three weeks I hadn't much spare time because I've participated in two chemistry contests, one of them being the Romanian National Chemistry Olympiad, from where although I've returned with an Honorable Mention, I still can feel that I could have done better.

The team members from my county (all seven of us) in front of the Palace of Culture in Arad, just after the ending ceremony (I am at the leftmost).

The other is ChimeXpert, an international chemistry contest (well, just Romania, Hungary and Italy will participate this year) in which I've qualified for the last phase, the international one. It will take place on 27-29 of March, in Satu Mare. Here I will take a written test that is worth 60% of the total mark and I'll have to present an original paper about applied chemistry (this part values 40% of the final score). So for this, I'll research for some interesting information and definitely try to use some creativity.
January 28, 2009
10:24
The Manganese Rainbow
» ‎ A Chemistry Question, Daily
As you may well know, manganese salts are generally black or gray. At the first sight manganese salts do not appear to be very interesting. But at a closer look, this element won't appear so boring. Actually, I can easily say that this is one of my favourite elements for some of its particular reactions. Yesterday, while illustrating redox reactions, I had the opportunity to make one of manganese's most fascinating experiments.
The first two attempts went totally wrong, and when I was on the verge of succumbing my positive state and just give up, the farewell try went just marvelous. It's a very coloured experiment that you definitely shouldn't miss.
Glassware you need: one 100 ml cylinder; one 600 ml beaker; stirring rods; a burete.
Chemicals you need: 500 ml NaOH 6M; H2O2 0,1% (you can obtain it by dissolving 1 ml of pure H2O2 into 350 ml water); CH3COOH 6M; 0,05 g of KMnO4 dissolved in 1 ml of water and ice
How to do it: in the NaOH solution chilled at 0^oC the entire quantity of permanganate is dissolved. Then from the burete 1 ml of H2O2 is added under continuous stirring. We can clearly observe now a palish green colour, because of the MnO4^2- ion. The reducing agent is H2O2.
2Mn⁷⁺O4^-(aq) + 2HO^-(aq) + H2O2 → 2Mn⁶⁺O4^2-(aq) + 2H2O + O2
You continue both adding H2O2 and stirring the upper layer of the substance until it gets cold blue.
2Mn⁶⁺O4^2-(aq) + 2HO^-(aq) + H2O2 → 2Mn⁶⁺O4^3-(aq) + 2H2O + O2
On the top you should add now the CH3COOH, slowly and continuously stirring. Around 20 ml would be more than enough. A crimson red colour should be now observed due to the reaction between the hydronium and the trivalent permanganate ion previously formed.
In the end it should look like this:

Tips:
1. Use only chilled NaOH
2. Do not use indecorous proportions of the substances! Follow the gravimetric instructions as close as you can for an accurate result.
3. When you mix, try to mix only the upper layer in order not to spoil the colours.
4. Have fun doing this!
January 27, 2009
9:26
Persil, an inorganic detergent
» ‎ A Chemistry Question, Daily

Hi there again! I have indeed said that I will no longer post until the Chemistry Olympiad, but today while looking at a video about the chemical element Boron, I heard the fact that Persil is an inorganic detergent that has his name inspired from its two main compounds : sodium PERborate and sodium SILicate. So I did a little bit of research on the Internet and may I say that, I've found some pretty worth to mention things. As I said earlier the two principal compounds of Persil are sodium perborate and sodium silicate. The major role of the perborate, in the washing process, is to decompose at high temperature in the washing machine in the presence of water to form hydrogen peroxide, and a B(OH)4^- ion. In the next step, the hydrogen peroxide will remove the stains by oxidizing them and making them more soluble into the hot, boiling water.
A little bit of History Before the first world War, there were no detergents commercially available. Women had to wash clothes with house made soap in the water of the nearby river (only rich people could afford their water pumping system).
Image from [www.hohenstein.de]
So, in 1907 Henkel started to commercialize the first detergent which was named after the two major components. This was to be one of the revolutionary inventions at the beginning of the XX-th century. But its great success wasn't felt immediately. Many people couldn't afford it, and it became popular only after the First World War, because it was widely used to wash the soldiers clothes. So only after that 4 years Henkel could lower the price in order to make it accessible to most of the people.
Original advertising poster
Nowadays, Persil is one of the very few toatally inorganic, commercially available washing products left on the market, that is widely used in Europe; the situation has pretty much changed in the last 100 years.
See you next time!
January 13, 2009
9:01
The Romanian National Chemistry Olympiad
» ‎ A Chemistry Question, Daily

Hi there again! Sorry for not writing for more than 2 weeks now, but I have been very busy with the chemistry Olympiad two Saturdays ago. I can say that I am very happy with my result, because I've managed at this point to qualify at the Romanian National Chemistry Olympiad, which takes place at Arad this year.

Because of the fact that the Olympiad is so close, and I have to learn a lot of new things in just 1 week, my chemistry teacher, Lidia Minza, gave me a few days off from school, in order to exercise some high-level problems, and to revise both theoretical and practical key aspects of Inorganic Chemistry, also mentioned in the Syllabus for the Olympiad.

So, see you after the Olympiad!
January 03, 2009
13:58
ChimeXpert Contest, First Phase
» ‎ A Chemistry Question, Daily

Today I have seen the results for a chemistry contest I have participated in. The contest is called ChimeXpert and it is an international contest, organised by Romania (you can participate by registering at this link [www.chimexpert.ro] and paying a fee of 12 Euro)

I've taken 247.5 points out of 300, which means that I correctly did 82.5% of the whole test. I was positioned first in my county, Galati, but I am pretty dissapointed because I have had higher self-expectations. Although my place in the county ranking may sound good, in the national classification I am only the 107th out of 282. In other words I am situated in the first 37.94%. I want to congratulate my classmate Andreea Stroia who obtained the same result as me.

The contest has taken place on-line, without a certain timebound and that means that participants could collaborate between them and even teachers could solve the problems for the participants. Even more, around 5% of the problems have been asked, in my and my teacher's opinion, wrongly (with none of the options correct - it is a 5 given options from which only one is correct test).

Now it is certain that I will pass to the next phase, but if I want to go to the international phase, I have to prepare myself a lot more because only the first 10% of all participants will pass.

With this post I invite anyone interested in Chemistry to participate in the following years, in order to make this contest truly international (I think many of my readers are high-school students or teachers).
January 02, 2009
8:23
New Year Chemistry
» ‎ A Chemistry Question, Daily
Happy New Year to All! I am going to talk in this post about Fireworks Chemistry, a very interesting subject may I say, with lots of Redox equations and thermal decompositions.

Image from [www.photoshopessentials.com]

You surely have observed that fireworks are coloured in different ways: yellow, green, red, blue, purple, white and even more colours. A specific colour is produced when a metal or one of the metal's salts is burned into the air violently. In this way one metal or any of it's salts at the same oxidation state give the same colour which can be described as following, as a result of a very common flame test.

Element Flame Colour

Li⁺ Crimson red

Na⁺ Yellow

K⁺ Violet

Ca²⁺ Orange Red

Sr²⁺ Red

Ba²⁺ Dirty Yellow

B^3- Green

Cu²⁺ Green

Video from: [www.youtube.com]
There are 2 characteristics of fireworks that are worth to be mentioned:
1. Incandescence (light produced by heat)
2. Quality
Generally, nitrate salts are used for fireworks, due to their instability, and light weight. For the igniting mechanism, phosphorus is preferred. Also, when we talk about fireworks there are two main igniting systems: in steps and all at once. Both need an initial explosive in order to make salts burn and after that shine is diverse colours. This substance is generally an ammonium salt due to it's instability and explosive properties.

A two step igniting system Of course, what I presented is only a very vague description of the phenomena, because I didn't include reactions or more complex diagrams, in order just to create a general impression about the subject. I can only now wish you again a Happy New Year!
December 28, 2008
7:19
Answer to: A mind snapping quiz
» ‎ A Chemistry Question, Daily
Two weeks ago I posted a quiz about a reaction that I considered interesting. Its text is the following:

You have some chlorinated water. To the solution you add some sodium nitrate, but not in stoechiometrical amounts (the sodium nitrate is fewer than it is necessary to react entirely with the mixture). The reaction products shall be:
1. Sodium hypochlorite and nitrogen dioxide
2. Nitric acid, hydrochloric acid, hypochlorous acid, kitchen salt and sodium hypochlorite
3. Sodium hypochlorite, hydrochloric acid and NO2
4. Nitric acid, sodium hypochlorite, hydrochloric acid, kitchen salt and hypochlorous acid
5. Kitchen salt, oxygen and hydrochloric acid
From the early beginning we can see that we have "chlorinated water". This means, that when we bubble chlorine into water the following reaction can be observed:

Cl2 + H2O → HClO + HCl

Next, we pour some NaNO3 into the solution. This means that the hypochlorous acid (HClO), and the hydrochloric acid will react to form nitric acid and sodium salts:

HClO + NaNO3 → NaClO + HNO3 HCl + NaNO3 → NaCl + HNO3

Because of the fact that the initial mixture is in excess, in the final solution will remain HClO and HCl too, but not even a drop of NaNO3.
To sum up the compounds of the final solution will be :
- HClO
- HCl
- NaClO
- NaCl
- HNO3
So the correct response is the fourth variant
I have seen that only 5 persons have answered to my quiz (from which only one of them has responded correctly), although I had expected a lot more to react. I know that this may be explained by the Christmas period that we are passing through, and people are more implied in celebrating this event in family than looking on chemistry blogs :-), and also by the fact that my blog is pretty new and hasn't got many followers yet. Merry Christmas and a Happy New Year!
December 26, 2008
6:37
Hydrogen Peroxide and Ozone
» ‎ A Chemistry Question, Daily
Three days ago, while I was reading an article about Oxygenated Water (H2O2) and Ozone (O3) chemistry, I saw 3 different reactions between the same substances mentioned above, all three possible. The reactions were:
1. 2H2O2 + 4O3 → 2H2O + 7O2
2. H2O2 + O3 → H2O + 2O2
3. H2O2 + 3O3 → H2O + 5O2
I let the book down for a minute and asked myself why: "Why all three reactions are possible?". Immediately, I realised that the first one is the sum of the last two; so, all I had to do is to prove the last 2 reactions.
1. H2O2 + O3 → H2O + 2O2
2. H2O2 + 3O3 → H2O + 5O2
From these two we deduce that the first one is also plausible. And that's it: All three are true!
December 22, 2008
13:41
An illusiory paradox
» ‎ A Chemistry Question, Daily

Because the Chemistry Olympiad is on 10 January and there is very little time left, I use the winter holidays for training myself for the Olympiad. It was 11 o'clock and I was solving problems from a collection of more complex exercises, when my attention fell on one entangled question. It said: In a closed recipient heated at high temperature, ŋ particles are introduced (ŋ is a natural number). In the same conditions are introduced ŋ particles more, and it is observed that the pressure remains the same. Explain the phenomena. The first thing that crossed my mind was the ideal gas equation PV = ƞRT. This meant that the pressure, and volume remained the same, so the temperature lowered. But immediately I saw the part of the text that stated that the conditions remained the same. I had no inkling for, let's say, about half an hour, although I was endeavoring to find the explanation. Finally I gave up. I looked at the answers part of the book and what I saw shocked me by it's unexpected simplicity We know that the pressure depends on the number of collisions of the recipient's wall with the particles. That means that if the pressure is constant , we have the same number of particles (in the same conditions). You may say now: "What? But we can't have the same number of particles because we added more. It's a paradox!". Yeah! You're half right, but you neglected a very important aspect of chemistry. Particles react with each other. Nobody told you that the particles we introduced the first and second time were of the same type. So here's the explanation: The first particles (A) reacted stoechiometrically (they were echimolecular) with the second set of particles (B) as following: A + B → AB. We had initially ŋ particles, we added ŋ particles, and in the end we had ŋ particles. The simplest reaction model of this type that crosses my mind is Mg + S → MgS.