apathy

in what reaction?

what's the mechanism? is it a substitution (of the chloro)?

What's that GRE chemistry anyway? Some "US/UK only" thing?

GRE stands for Graduate Record Exam. It's a typical requirement for graduate programs in the US. There's a general one and various subject tests also. The general one is a breeze and the subject ones are really tough.

The chemistry GRE is hell. I took it a few years ago.

It's really heavy in organic synthesis and physical chemistry. Some of the questions were really just pure physics. They have complicated analytical questions that don't have too many round numbers and they wouldn't let me use a calculator, so half the time I was taking the test, I'm sitting here doing long division. It's really light on inorganic which is my strong suit, and the pchem, like I said, was always obscure.

The organic questions are ridiculous. It'll be something like, "which set of seven reagents in four steps will NOT produce the above transformation."

Anyway, if you don't have to take it, just don't bother. It was humbling for me. But maybe you are a genius and are not swayed by such talk.

structure of poly[dimethylsiloxane]

Just in case anyone cared.

Oh! I forgot plasmon resonance! If you have a colloid of a certain metal, usually silver or gold, you will see different colors in the solution. The color of the solution depends on the resonance of electrons on the surface (plasmons) of the metal particle. The frequency of the resonance is dependent on the size (and shape) of the particle.

You can make a rainbow of different colored colloids of, say, gold. From pink to red to purple to blue, all depending on the size of the particle.

Ok, you don't need less than 10 d electrons to have color. For every molecular bonding orbital there is an antibonding orbital. If the transition to that orbital is low enough in energy to be promoted by a visible photon then you will see color. There are plenty of d10 complexes with plenty of color. You also don't need the antibonding orbital if there is an available orbital on the ligand. Or an electron can go from an orbital on the ligand to one on the metal. MLCT (metal to ligand charge transfer) and LMTC (ligand to metal charge transfer).

You don't need transition metals for color, obviously, as there are many colored substances that do not contain metal. All you need is a an electronic transition in the visible region. I think there is another thread about colored smokes. He asked about p-nitroaniline, which is red and there's no metal in sight.

it also makes a nice intense white flame, good for flash bulbs and the like

edit: oops, bud... already said that

There is no easy way to store HF' date=' it reacts with virtually everything.

It can even dissolve glass.[/quote']

 

Funny, I must not have the Nalgene bottle of HF under my hood.

actually, it's a little more complicated, this question isn't as easy as it seems

First: you need to look up the latimer diagrams for standard redox potentials for both peroxide and permanganate and see what the products may be formed from the reaction (acidic or basic media differ, there will be separate latimer diagrams, but they should be in the back of your textbook)

Second: a good way to do it is to write out the reaction and balance it, electrons, charges, and all

here is a good step by step: http://www.science.uwaterloo.ca/~cchieh/cact/c123/balance.html

balancing redox equations: anyway, write and balance the 1/2 reactions, then balance H's with protons (for acidic media), then balance the O's with waters, balance the charges with electrons

then multiply the coefficients in the reactions so that the number of electrons are equal on both sides, then cancel out all the electrons, and whatever protons and waters are left, add the two half reactions and you now have your balanced redox eqn

from the coefficients you can get the number of equivalents of peroxide per permanganate (lots of pers)

I couldn't give you the answer because I don't know if it's in basic or acidic media, so I can't predict the products.

I would just like to back up what apathy has stated as it answers the question. Some people might be a bit confused by the terminology.

 

Now of course if you place some lithium in water' date=' it will not have as violent a reaction as sodium which will be less than potassium and so on to cesium having an extremely violent reaction in water. This is due to that electron being "ripped off" of off the cesium. That being so because cesium has the lowest first ionization energy, making it the easiest to lose that electron.

 

Lithium on the other hand is the strongest reducer (as far as elements go). That is why it is topping those reduction potential lists. If you want an extremely strong reducing agent, then you go to LiAlH4 - and there is your lithium.

 

And so because lithium is a stronger reducing agent than potassium, a reaction such as Li + KNO3 --> LiNO3 + K (as shown in the experiment done by David Hahn) will in fact work.

 

I hope this has helped a bit to explain.[/quote']

 

 

Well, in lithium aluminum hydride the reducing agent is AlH4- and lithium is just the counterion.

 

well I`ve been informed that sodium will also make a nitride and so will potassium even easier! than lithium will' date=' and with much less energy involved

 

 

as for a reducing agent, sodium amalgam will kick ass outa your Lithium Aluminium Hydride ;P[/quote']

 

Yeah, any alkali metal will beat any metal hydride that I can think of.

NaK alloy can be pretty ugly since it's a liquid at room temp, it can go spilling everywhere looking to start a fire.

wow, cool

from these responses I definitley understand much better now

it seems that there are many factors (as to be expected) that influence intellegence

and it even seems that brain size may be one of them (but not at all the major one)

i never thought there may be a difference in nerve conduction among individuals

maybe the people whose brain waves are "high quality" , or more efficient anyway, have a more well-constructed "schema" or something like that, that may have stemmed from early childhood development? maybe they were more mentally stimulated in the early years of childhood? that would tend to compliment the genetic side of things a little i suppose

anyway, i feel much more informed about it...

thanks again!

more connections makes sense to me

woops

that last post from yourdad... got in there before i hit "post"

well, i didn't expect to get answers that were that good

thanks a lot! it makes more sense to me now

i suspected that it had a lot to do with brain size to body size ratio, since I have heard that the brains of wolves are proprotionally larger than those of domestic dogs because they have more to remember about their social order and hunting strategy, etc. while domestic dogs were thought to have originally been slightly social scavengers (at least this is what I've read in mags)

this is still implying that brain size has something to do with intellegence, even if it's relative brain size

about the neocortex and gyri:

is there such a strong relationship between the number of gyri and intellegence?

i mean if we cracked open the skull of a genius and one of a person considered "slow" could we count a difference in gyri? or is it just an average difference across species?

and this is saying that the size (or relative size) of a certain part of the brain has to do with intellegence

i can see that intellgence must have something to do with the presence of the neocortex, this says that the 'wiring' is important, of course

then increased intellegence comes from an increase the relative size of this part?

does more intellegence stem from having more neurons? bigger neurons?

i'm trying not to oversimplify it, but it's tough

The Gods Themselves by Isaac Asimov had creatures of 3 sexes

We are shown ancient humanoid skulls and are told that cranial capacity increased as humans evolved. It is also inferred that this increase in brain size corresponds to an increase in intellegence and learning ability.

But, certain animals, like domestic dogs, come in all shapes and sizes. A very small dog with a small brain can often be more intellegent than a large dog with a large brain. This would tell me that the dog's intellegence has more to do with "wiring" than size.

Also, some parrots have demostrated the ability to learn concepts and adapt them to speech. Not just "parroting" but answering questions like "what color is this?" "green" and their brains are no larger than a peanut and not specifically wired for human-like speech.

Could someone please explain this to me?

oo oo

before you latin guys leave can I ask a question?

it has to do with the literal translation of:

"Novo ordo seclorum" from the great deal of the US

novo = new

ordo = order?

seclorum = ????

what does this mean?

wow, i looked it up and iridium is quite a bit cheaper than platinum per ounce, much to my surprise

http://www.platinum.matthey.com/prices/

For July Pt=$811/oz Ir=$207/oz 811 is the highest i've ever seen it!

But, buying isotopically enriched Ir would be a different story.

Not to mention paying for beam time at a neutron source.

eh, you can throw fullerenes into the graphite pile, since it's just glorified graphite anyway

one thing about graphite is not it's hardness but it's "toughness"

along the x,y (in the graphene plane) graphite is very very strong

that's why members of our group make nano-sized graphite plates and blend them into polymers, if you have the platelets covalently bound to the epoxy resin, it increases the toughness (and Young's modulus, etc) quite a bit (and makes it black)

beta-carbon nitride is predicted to be harder than diamond but it has yet to be synthesized in more than a monolayer or two

http://encyclopedia.thefreedictionary.com/Beta%20carbon%20nitride

http://www.campusprogram.com/reference/en/wikipedia/b/be/beta_carbon_nitride.html

here is a very simple way using KIO3, KI, and starch.

http://cas.bellarmine.edu/chem117a/lab/vitamin_c.htm

you can't just ask what's the equilibrium equation of sulfuric acid

do you just mean the equation that represents the dissociation of sulfuric acid in water?

you were given the pKa's of sulfuric acid, judging by your response, you didn't know what they are

the "p" function is just the negative log of something. pH is the negative log of [H+] , the concentration of protons. pKa is the negative log of Ka, the acid dissociation equilibrium constant.

plug -1.92 into your calculator and hit 10^x (or inverse log), that number is Ka.

Ka = [H+] / [HA] , [H+] is the conc. of protons that have dissociated and [HA] is the concetration of the acid that didn't dissociate, that ratio is Ka.

Since sulfuric acid can donate two protons, there are two equilibria to deal with and two Ka's.

Google "Henderson-Hasselbach" (+ "equation").

Oh, if the slabs are water soluble then it just sounds like your just getting bigger crystals than you planned and it all caked together in the vessel. I don't see why your white rocks or slabs wouldn't be what you want (ammonium sulfate) or a mixture of that and ABS. And sure, ABS could surely get to AS with one more equivalent of ammonia (or even an excess of ammonia). Once the water and excess ammonia are driven off you should have solid AS (b/c sulfate has a -2 charge and no higher). If it's a powder or not just depends on how wet it is and how big the crystals are, based on my experience.

If I ever want to make the ammonium salt of an anion, I just react it's acid with excess ammonia, heat (if poss.) till I can't get any more ammonia out of it (on small scales just by holding pH paper over it and seeing if the vapors are still basic). Then I try to evap. the water somehow. Any leftover ammonia will leave before the last of the water. Ammonium stays behind with the anion leaving you with the salt. Should work for sulfate just fine.

Why can't you buy the K from Aldrich or Fisher or some supplier like that?

They'll sell you a big ol' jug of chunks in oil.

There must be some kind of restrictions I guess, on who they sell to.

But I would try calling them up, or registering on their website and creating an account. Make sure that you are "representing an organization" and intend to use the products for research purposes only. It's definitely a Haz-Mat, but I don't see why they wouldn't sell it to you. Maybe I'm naive in such matters.

what's a sig image, and no, i guess i don't see it...