Comandante

It depends on what level of chem you are If you're just starting on hybridization and all that, then there are a few general rules, well more like, memorising and being able to explain some examples. But if you need to work these out yourself for a test or something then there are a few more examples.. and rules First thing would probably be to determine the shape of the molecule and then hybridization. Typical example would be nitrogen, which has 5 valence electrons, I've usually seen it bond with 3 other atoms and has a pair of electrons spare. This pair of electrons acts almost like another bond, but a bit stronger (repelling). What happens is that you need to determine the angles around the central atom at maximum spacement of other atoms in the molecule. And for the nitrogen I mentioned, the angles would be somewhat less than 109.5° - this they refer to as sp3 hybridization (exception would be N in amide bond, where it was experimentally found to be sp2 hybridization rather than sp3 by this guy: http://en.wikipedia.org/wiki/Linus_Pauling ). Basically to determine the angles you just have to work out where the atoms will be located when they push apart in space around the central atom, taking into acount valence pair of electrons such as that in nitrogen. For more accurate/detailed description of that refer to the http://en.wikipedia.org/wiki/VSEPR . For more info on hybridization.. again, refer to our almighty wiki ; http://en.wikipedia.org/wiki/Orbital_hybridisation

sorry I don't know scientific name for that one huntsman is it?

yes, as I mentioned, it's this spider; http://en.wikipedia.org/wiki/Image:Huntsman_spider_on_log.jpg (that particular specie on the photo, I have one that's 99% identical)

thanks. I'm also trying to find out how long can they be without any food at all? I hope I don't have to go practical on that one... harsh isnt it

Yeah, it's one of those; http://en.wikipedia.org/wiki/Image:Huntsman_spider_on_log.jpg .. It's about 4cm in diameter and I have no intentions to release it just yet

Do you need exact values for angles or? This is going to be a guess, but looking at the molecule on wiki I would say that bond angles around carbonyl carbon are 120° in sp2 hybridisation as well as around nitrogen on alpha position.. if I remember correctly, 120° too, in sp2 hybrid. As for intermolecular forces I would guess there would be hydrogen bonding as hydrogen is bonded to decently electronegative element - N, and N can provide pair of electrons. As for properties.. well it melts at 68°C, I'd say this compound is 'fragile' if you can relate to that but I think you need to explain it in terms of forces etc... Hope that gives you some hints. Back to my math now exam tomorrow!

a few questions regarding spiders in general; first of all, how long can they survive without any food? i know they can eat their own protein that they usually use to build webs... more on this would be helpful. secondly, what are some of the insects that spiders in general will tend to avoid eating? also, do they require water and in what amounts?

Ah I see. He confused me by saying "Now the treatment doesn't work" part, I had the idea he was saying it now doesn't work for anyone, otherwise I see what you mean. That sounds right now Thanks.

I don't understand how that works. How did cancer cells get immune to that specific drug or treatment in other patients when other patients haven't been treated with the drug? You were referring to any patient when you said ALL cells , no? I find that rather interesting.

Hey, that sure is a nice deal! I might consider it, though I've recently been in contact with a reseller from China who has some nice deals too, but he ships dyes in solution (as those in light sticks) already so I'd have to work out whether concentration is worth it as compared to that site of yours. But since they accepts paypal too, I'll definitely look into it, and also because they say "The dyes in this kit are some of the most intense dyes known, many visible at parts per million concentration." and so as little as 5grams would be quite plenty as you say! Thanks!

Well you could say it's a bit unfair yeah, but aren't you on our side I think it's the quality of members that make up the 'strength' I was referring to. I think that we have more specialists in different areas while majority of their specialists would be in phys/eng. It's true though, if we compared physics only, they would outweigh us probably, but then again, SFN is not 'PFN'. When you access forum statistics, can you see number of words in the entire database? If you could compare that to theirs you would get a much better estimate of the 'strength' for the period of.. last 5 years? And I would definitely agree on that homework part, probably half of their members are hanging in the homework section asking for help, it's almost like 'free lunch'. I'm having an idea that forums should be more forward-pushing if you will, in a sense that things to be talked about would mean new ideas rather than answering same homework question all over again in a different context. That's another reason why I would place our 'strength' in a good position. The age of the forums would be another factor to consider. When did SFN come to exist and when did physicsforums? If SFN is older then physicsforums must've done a hell of a good job getting those members. But then again, I'm sure the main attraction was the homework help section. I could be wrong yes, simply because I don't visit physicsforums very often, but I did check it out briefly, hence the reason I wouldn't want to carry my point anywhere further. Just my personal view of things. If I go and make an account though, I'd probably get a much better picture in a year or so Perhaps they could help me with some of my homework too

True. Or we would hope that was the case I personally think SFN is much stronger than physicsforums, due to the variety of other topics rather than just physics... Either way, I would think there are a lot of same members registered on both..

Sometimes it's interesting to see places where SFN is referenced http://www.google.com/custom?domains=www.wholinks2me.com&q=www.scienceforums.net&sa=Google+Search&sitesearch=&client=pub-1596829452635297&forid=1&ie=ISO-8859-1&oe=ISO-8859-1&flav=0000&sig=xz8IPeIrBZCNsOPR&cof=GALT%3A%23008000%3BGL%3A1%3BDIV%3A%23336699%3BVLC%3A663399%3BAH%3Acenter%3BBGC%3AFFFFFF%3BLBGC%3A003366%3BALC%3A0000FF%3BLC%3A0000FF%3BT%3A000000%3BGFNT%3A0000FF%3BGIMP%3A0000FF%3BLH%3A50%3BLW%3A230%3BL%3Ahttp%3A%2F%2Fwww.wholinks2me.com%2Fimages%2Flogo.gif%3BS%3Ahttp%3A%2F%2Fwww.wholinks2me.com%3BFORID%3A1&hl=en Having looked at that I came across an interesting link; http://www.physicsforums.com/showthread.php?t=79299 It appears as if our colleagues on physicsforums think SFN sucks lol

That's the one! Thanks.

insane_alien, whatever happend with taurine and guarana on your list

sodium phenolate..hmmmmmmmmmmmmmm by the way YT, I once came across one of your posts where you referred to a website that had list of products you could pick and what they contained.. I hope you know which one I mean.. if you do, could you please post it here again

Interesting. The question is: how difficult is it to manage it?

Commercially, contact process is used. Sulfur trioxide appears in the contact process, however it is converted to oleum first before reacting with water to give sulfuric acid, as YT said. I don't recall any texts where SO3 reacts directly with water to give sulfuric acid, though it doesn't sound too fantastic, perhaps it can work?

Atomic radii don't decrease as you move from right to left, atomic radii generally decrease as you move across a period from LEFT to RIGHT and they increase as you go down the group. The reason why atomic radii decrease as you move from left to right across a period is that the number of protons increases by 1 per each step across, this causes increased nuclear charge and attracts the outer electrons more strongly towards the center, hence decreasing the radius. The atoms with the largest atomic radii are located in Group 1 and at the bottom of groups. I don't have a lot of time now but here are some sites to help; http://www.chemguide.co.uk/atoms/properties/atradius.html and this table; http://www.crystalmaker.com/support/tutorials/crystalmaker/resources/VFI_Atomic_Radii.jpg

Interesting. I'll read over it later, I'm revising for exam too right now

Last night I came across something that said that phenol was once obtained from distillation of coal tar. Is there any practicality in this for the home scientist? Coal tar sounds heavy though, I'd guess you'd probably need some serious distillation to get phenol out of it no? Does anyone know the process? (And how to get coal tar:-) ) On the other hand, it again seems easier to obtain benzene... if anyone comes up with any ideas let us know, I'd be very keen to get my hands on benzene or phenol

General diagram for the Death Ray didn't disappear because he used it as an ad to offer full schematics for sale to various governments. Some were interested, most notably Soviet Union and UK (while US probably hoped to get it for free), but nobody wanted to proceed with the deal. However in-depth details were either not found or not released - it is not known what really happened because all of Tesla's documents were seized by the FBI shortly after his death and although most of them were later returned, there is strong evidence to suggest that a good sum of the documents is still missing. Also, I think it says in one of the documentaries I listed that UK attempted to make their own beam weapon based on Tesla's ideas but failed. (a bit about Death Ray; http://www.pbs.org/tesla/ll/ll_wendwar.html ) FBI has a page on Tesla and the whereabouts of his papers; http://foia.fbi.gov/foiaindex/tesla.htm

What an idea!!

Yes, this is the method of initial rates. What happens is that at the start of reaction there is insufficient product for any drastic effect a reverse reaction may have, hence initial rate of reaction is taken and it is a tangent at point of time as [math]\Delta t\rightarrow 0[/math]. When you have varied concentrations of different reactants for multiple retries you can get different initial rates of reaction. This will be useful in determining experimental constants a and b in [math] Rate = k[A]^a [ B]^b [/math] where A and B are reactants (in this example only 2 reactants) in that you will be able to use different rates and then comparing each with 2 different experiments. For example; in 2 of the experiments you would've varied concentration of one reactant while keeping other the same, you can use this neatly to do a ratio equation such as: [math] \frac{Rate_1}{Rate_2} = \frac{k[A ]^a [b ]^b}{k_2[A ]_2^a [b ]_2^b} [/math] in which you can cancel out either A's or B's depending on which one you kept the same for those two experiments. You also cancel k's. Then you get fraction of [math]\frac{rate_1}{rate_2} = [A]^a[/math], multiply both sides by natural logarithm, ln, and you'll get your 'a'. After you get your 'a' (which is usually an integer 0, 1, 2 or a half - this also determines the order of reaction with respect to A, but not the overall order) you can use it in conjunction with other 2 experimental retries to figure out 'b'. However, if you have another 2 experiments where you varied concentration of B but kept [A] the same then you can use that as well; again, [A]'s will cancel, along with k's and you get your b. Then you rewrite your rate equation with known constants of a and b, hence you determine the overall order of reaction, and then you can use one of the experimental results (one only!) to find out what constant k is as you will by now know both 'a' and 'b'. When you find k you rewrite the equation again with k in it. You can then test this rate equation to see how it fits by substituting various experimental results. That pretty much sums up the initial rates method for determining the rate equation.. I hope. And as a further note: all of the above is for a plot of concentration vs time. I'm not quite sure what you're referring to, maybe you can clarify.

There have been a lot of threads about Tesla on these forums (I started one myself few years back: http://www.scienceforums.net/forum/showthread.php?t=8529 highlighting Tesla's contribution to science). A lot of those threads have some serious flaws and misleading information and before you take anyone's opinion as a fact on anything please make sure that you confirm this by reading some acknowledged sources. Tesla has even been labeled as a quack, on these forums... and in general is considered as a side-push if you will, to the scientific development. This is hugely disappointing, ignorant and disrespectful. If you go on and read some of Tesla's work you'll see why. He contributed to almost all areas of science though most of his patents had foundation in physics (http://en.wikipedia.org/wiki/List_of_Tesla_patents ). He was close to Nobel Prize but that's a completely different story. Had he received it when he should've he would've probably been more respected these days. You can check these stories out in many books or good sites. Here are some interesting things to look into: Documentaries: Nikola Tesla; Genius Who Lit the World (1994), Nikola Tesla: Master of Lightning (PBS, 1999). Books: compiled autobiography (free); http://en.wikipedia.org/wiki/My_Inventions:_The_Autobiography_of_Nikola_Tesla also Tesla: Man Out of Time, (there are more!) Generally, if you read/watch only these I mentioned you should have a very good grasp of who Tesla was, what he did, when and how. If you want to know more I'm sure you'll find some, be cautious of sources though. There are millions of sites around the net claiming that they succeeded in harnessing the so called 'free energy' that Tesla apparently was looking for... It's not even funny. Some of the documentaries may be available on Google videos