/sci/ - Science & Math

how do i molar mass

Why don't you help the Australian guy in the other thread looking for Potassium Perchlorate?

>>5132284
I fear the government owning me.

>>5132273
Use the mass number of the perodic table for each element. Multiply this by the number of elements you have. Take their sum.

For example methane CH4's MW would be calculated by:
#H atoms * atomic weight of H + # C atoms * atomic weight of C;
4 * 1.00089 + 1* 12.011 = 16.015 amu

>>5132289
ok thanks now how do i pv=nrt

Hey, awesome, hang around, I'm working on a journal on enthalpy & similar. Might have a few questions, let me just read my work. Also, thanks OP - to keep you occupied; what are your current profession, and what makes you able to give others help in science (e.g. what level is your chemistry-knowledge on?)

Which branch of chemistry deals with explosives? I always thought it was inorganic but a friend of mine is saying its organic. Help us settle an argument

>>5132302
lol I have been coming to this board for a while but have never gotten this question.

I am currently a PhD student in computational chemistry. I have been teaching chemistry as a teaching assistant since my second semester of undergraduate.

Check out my facebook and youtube crap is bored.

http://www.youtube.com/user/TutorChem
https://www.facebook.com/chemtutorsimpson

>>5132305
lol I would actually say it is physical chemistry that blows must stuff up.... maybe even materials science...

>>5132296
PV=nRT is pretty simple, just make sure your units are correct and plug and chug.

Depending on your gas constant (R) you need the units of all of your other units to match.

If you have a more specific question I can help you out.

>>5132315
Thanks OP in return here's a snazzy periodic table

Where do I start if I want to learn chemistry?

>>5132318
ok how do i electronegativity

>>5132321
It depends on how basic and what type of learner you are. I say just grab a basic text book, and try to learn that way. From there if you get stuck bug this board, or check youtube. If you want to get credit for it though, just take a class at a local university or community college.

>>5132312
>computational chemistry
Another evidence that we only have theorists on /sci/.

>>5132325
Thanks lol

>>5132340
lol Yeah. I am at a computer all day so it helps. In my undergrad though I did environmental chemistry where I synthesized PCDEs and ran a G/MS all day lol

>>5132327
Electronegativity is related to atomic radius. For a review of this check out this youtube thing:
http://www.youtube.com/watch?v=qnSyZfzU2_g

Otherwise EN can be used to predict what atom will be taking or giving electrons. THe left of the periodic table is less electronegative, the right more highly EN. The higher the EN the less likely something is to give up and electron while lower leads to something giving up an electron. Linus Pauli did a lot of work on this stuff.

>>5132325
SAVED THAT BITCH!

Would you say the "chemistry tradition" has been lost now, and chemistry is just a field like any other?

Let me precise what I mean: I'm a physicist. Once, a chem prof. in Japan gave us a fairly old paper (can't remember the name) where the author tried to convince physicists of the utility of a chemist's intuition. It had mostly to do with molecular chain, he explained how a chemist could easily find what a physicist would have to compute.
Chemistry had its very own development path and tradition as a scientific field, descending from alchemists and so on.

Do you think this has disappeard and chemistry became "yet another branch of physics" or do you still do things your way?

>>5132302
Neat! WHat is the focus of the journal?

how do i turn shit into gold?

>>5132373

eat more gold

>>5132369
lol THis is Roald Hoffmann's review on a 1D hydrogen chain, isn't it?

No I do not. I currently work in the relm of surface physics, yet I am a chemist. I have given chemical insight using my intuition (along with calculations) to show that there is some benefit to having this chemical intuition. WHile much of materials science is doing this, if you walk up to any inorganic and organic chemistry lab you can still see that they draw orbitals out and things along those lines.

I hope this answered your question.

>>5132382
Also here are some of my journal articles on the subject. If you have access through your institution...
http://www.surfacechemistry.comeze.com/1_3_Publications.html

Still here?
>Mg(s) + HCl(aq) -> MgCl2 + H2
correct? but why is it MgCl2 and not MgCl

Ok OP. I've been looking through my results, and this question might be a little unorthodox.
You see, we were required to find molar enthalpy's for 5 ions. My results fit almost perfectly with the 'correct' result for 4 of 'em. However, the last one is off by 50%!
View picture for details; have I done anything wrong? Why am I using the heat capacity for water, when we used an acid?
If nothing is wrong, do you have any idea why I'm off so much? Anything special about this reaction?

>>5132390
lolz NIce gif.

TO answer your question it has to deal with the valence of Mg, Mg has two valance electrons that want to either bond with something or to be given to something. Cl has seven valence electrons, but wants eight (octet rule). Each Cl takes one electron each leading to MgCl2. Does this help?

>>5132399
>mfw my teacher tells me 2 hydrogens takes one electron each and bonds.

>>5132387
I see you use Turbomole.
Do you have to homebrew your own code from time to time?

>>5132398
Hrmmm you may need to elaborate more. THis might have something to do with the pH of your solution. Mg can react with OH- to form a sparing soluble salt.

There are actually a bunch of things that could be wrong. The value you get is not terrible though... maybe you could elaborate more. What other ions did you look at?

OP, what are your thoughts on chemical engineering?

>>5132407
Not usually. We are working on something to do it, and it will not cost anything but I hate coding and it takes time lol

>>5132415
It is great to get an undergraduate degree in. ANymore than that, and you will not find a job, or should have just used the time to get a business degree.

I had a physics minor and was considered to be a chemical engineer (as I took all the courses for it but my institution did not have a chemical engineering prorgram). I had many job offers in my home town that would have paid me over 60k... but I chose school because having worked for the places during internships I knew how boring the jobs would be.

I have a basic question; how do chemists get Sulfate in a reaction instead of Sulfite? Do they know based off the the known results of the experiment?

>>5132404
That is when it gets tricky.... It depends on how you think about it. The real picture is somewhere in between, and makes you actually think about what is a bond... Being a theorist I have an existential crisis once a week thinking about this stuff lol

>>5132431
It depends what type of reaction they are doing. FOr the most part it is assumed that it is sulfate because that anion is much more stable than the sulfite anion.

>>5132436
Thanks!

>>5132427

how do i use singular perturbation analysis to solve for the concentration profile of an impurity diffusing uniformly into a cylindrical medium?

teach me how to do acid - base redox reactions including half reactions etc. AP chem student

I need some help ITT:

>>5132444

thanks in advance

>>5132446
>singular perturbation analysis
lol Oh dear god. I have not done this in a long time.

Can you give me any more data than that? I remember almost nothing from fluid dynamics and diff. eq. It has been a good 5 years since then and I have never once used that stuff lol

Teach me the most applicable things about chemistry that occur in every day life. Like, what are 10 things you think EVERYONE should know about chemistry because they're so damn useful / important to life.

>>5132454
YOu really have to dive in the new literature for this one. Try the American chemical society web stuff for this one. Try to search for lanthanides and actinides complexes. Also you can use scifinder web to search the chemical structure of different compounds.

You may not find anything though. These compounds are on the edge of research currently.

>>5132450
Nice gif.

All you need to do is determine how many electrons are flowing for two half reactions, then for the overall reaction make them balance.

Some basic guidelines are that Oxygen always carries a negative 2 charge and the halogens almost always carry a -1. Oxygen only carries a -1 when it is in a peroxide. Other than that you can use the tables in the back of your book or reference table to help you solve the question

>>5132463
Thanks, I'm on it right away! It's my first chem course in uni though so I'm a complete beginner in this.. You say that these compounds are on the edge of research currently, what kind of research exactly?

>>5132457
IN no real order of importance

1) How Heme works
2) What orbitals are
3) How everything is just trying to be at lowest energy
4) Entropy is always increasing
5) Chemistry can be used to answer almost any question
6) Molecules are not static, they are constantly in motion
7) We currently do not understand water completely
8) How there are radicals floating in the air and without the hydroxyl radical nothing would burn
9) Quantum mechanics does not mean that there are endless posiblities (the word probability gives people the illusion that things are not completely determined by equations, I think everything can be explained in equations)
10) Molecular orbital theory has so much power to explain chemistry.

THere is a ton more, it is hard to localize this train of thought lol

>>5132456

yeah, don't worry about it then hahah, but thanks anyway. i can figure it out with the book, was just being lazy. /mondays

>>5132475
They are used in biochem to look at different binding sites of proteins:
http://www.chemistry.buffalo.edu/people/faculty/morrow/

Also in terms of nuclear waste:
http://ja01.chem.buffalo.edu/~jochena/research/research.html
Look at the heavy elements section here

As a computational chemist, do you ever explicitly solve the Schrodinger equation or do you do some sort of variational principle such as the Rayleigh-Ritz and merely approximate the lowest energy states?
Additionally, do you have to incorporate in relativistic effects?

>>5132457
Hess' law explains how we can say that what we know about combusting fuel in in the air can tell us about how much energy our body can capture from food.

>>5132483

I guess I meant more like, what are some things that apply to every day life. Like if I was doing x and happened to know fact y it would make the difficult of x much lower or the efficiency with which I could do it higher. Like knowing water will boil faster at a higher altitude for example when I'm vacationing in the mountains or something.

Those ten are pretty cool as well, by the way.

>>5132494
I use DFT (density functional theory) that uses the ground state electron denisty to predict various properties of the molecules/systems I look at. THIs was shown by W. Kohn that you can use the ground state electron density to know everything about a molecule similar to a wave function.
>>explicitly solve
Nope. It is impossible to solve the schrodinger equation exactly for anything beyond a one electron system. THis has to deal with something called the many bodied problem.

>relativist effects
Yes we do for the heavy elements. I usually only incorperate them when I investigate gold surfaces. You culd use them for simple systems without heavy elements for a more complete treatment of the system, but it almost does not change results for light atoms. Heavy atoms can change things a ton.

>>5132507
Ok.
1) Filling your tires with nitrogen does not save you money, the atmosphere is 79% nitrogen so there is almost no difference in the density of the air in your tires and that of pure nitrogen.
2) Chew wintergreen lifesavers in the dark infront of a mirror, you will see it glow.
3) Acetone will take off perminant marker, it is nail polish remover.
4) To burn something without leaving a mark (such as on a mirro) use rubbing alcohol.
5) Copper is very important for hair growth. Eat more copper is you want your hair to grow faster.

THinking of more...

>>5132508
>Yes we do for the heavy elements. I usually only incorperate them when I investigate gold surfaces. You culd use them for simple systems without heavy elements for a more complete treatment of the system, but it almost does not change results for light atoms. Heavy atoms can change things a ton.
What are we talking about hear? Do you add terms to toake them into account or do you have to pull out the whole formalism of Green functions?

>>5132520
A little of both.

We use the Dirac Hamiltonian with something called the Zeroth Order Regular Approximation (ZORA) to compute our energies and electron densities. We also have to include a correction in our basis sets.

It is basically introduction a parameter to take relativity into account

is there any REAL cure for baldness?

>>5132507
6) Use hot water when cleaning dishes, it will clean them more efficiently
7) When you chew aluminum foil with amalgum filling, the pain you feel is brought about by the electrochemistry occuring between the two.

... this is tough. I am a theoretician! I am not used to practical! lol

>>5132535
lol Maybe. My friend's father is a dermatologist and he says there is a lot you can do to prevent it. The science has come a long way.

>>5132544

Is there? My hairline is starting to go slightly, actually.

>>5132545
Yes. Go see a dermatologist. It seems weird because you think skin only with them.

>>5132224
Well guys, I am getting tired and have to take a nap/go back to work.

Check out my youtube page if you are bored or need any help. I will be here for about 30 more mins.
http://www.youtube.com/user/TutorChem

HOW DO I FIND THE STRUCTURAL FORMULA OF ANYTHING WITH MEANS AS PRIMITIVE AS POSSIBLE??

I think it would be cool to make a chemical clock, but one with an element that gains energy from light or an externally applied electromagnetic field such that the system avoids resting at equilibrium as long as the external energy source is applied. Not really sure where to get started on that other than general electrochemistry. I haven't looked into it that much, though, other than reading basic descriptions of well known chemical clocks.

Whats the cheapest alternative to a rotary evaporator?

On the off chance that OP comes back.

I want to work in biopolymer synthesis, I'm an undergrad right now taking OChem, should I minor in physics or MSE?
How much should I know about organometallic chemistry? I've been looking into Grubb's catalyst but a lot of these things go over my head.

Is polymer synthesis chemistry heavy? I really enjoy OChem and I'd love to be able to apply concepts I learn in my OChem class every day in research.