The Periodic Table - 2015-11-13

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1:21 AM

@TanMath @Jan @Ϻ.Λ.Ʀ. Thanks for the response, I'm just wondering what the reasoning & motivation behind placing a "stoichiometry" chapter, and a "reactions in aqueous solutions" chapter at the very beginning of an introductory chemistry book is. I've studied physics from first principles as best I can, so to me those two chapters look like they come out nowhere and should be placed a lot later in the logical flow of the book right?

They seem to me like topics which deserve to be discussed late into your discussion of statistical mechanics and are things that can be developed in more generality right? Where would I find those chapters discussed 'properly', i.e. placed at the correct point in time in the discussion? The only chemistry book I've found that really follows this plan is McQuarrie's Physical Chemistry, but from browsing it I can't make sense of my question.

Another thing that really bugged me when I tried to read a chemistry book before ever studying properly, is that in those chapters they just give you reactions like $H_2 + O ---> H_2 O$, this is a trivial example, but they give you crazy equations and I wonder is chemistry always going to be like this where you're given both sides, or is there any first principles way of predicting the products (e.g. $H_2 O$ in my example) from fundamental principles?

I think Organic chemistry teaches you a ton of heuristic rules you try to remember, right? Things like 'substitution reactions' so you apparently know how to predict something based on a few imputs, but how do I do this systematically I guess? Thanks!

@bolbteppa That's why there are these two chapters - it's the basics of reactions, at start you could ditch thing like statistical mech or quantum mech - if you want to predict reactions you have to know other reactions to make analogies. BTW you shouldn't ask about specific books I've never even heard about this book earlier

3 hours later…

4:40 AM

So here is the plan:

1. When the event, I probably won't be here, so do whatever you want to do, like retagging some recent questions.

2. I will come around 30 min later, where I will lead the TRE

We will do thermodynamics and acid-base...any other tag ideas?

1 hour later…

Martin - マーチン

5:46 AM

I am sorry, but I will not make it to the TRE tonight and the next two editions, too.

6:40 AM

0

Q: Mysterious upvotes

I'm talking about one recent question: Has a carbon compound ever been found having an ionic bond?. The question is quite trivial, so is my answer, and I expected it to get a modest sum of 2-3 upvotes over time. But 12? Flattering as it is, this just doesn't feel right. What kind of flashmob is t...

2 hours later…

8:19 AM

You can grow new brain cells. Here's how

2 hours later…

9:50 AM

0

Q: Area 51 proposal: Science Educators

I recently proposed Science Educators, a site where teachers and tutors of any field of science (chemistry, physics, biology, earth sciences) can ask questions. I decided to join forces with all sciences since Mathematics Educators is not getting sufficient traffic, therefore I considered it un...

2 hours later…

12:03 PM

@bolbteppa Chemistry does not lend itself as well to "first principles" as physics, so don't expect to have a first principles way of predicting products. As you learn more chemistry, you will learn more about which reactions are likely to happen, which reactions aren't likely to happen, which molecules are stable and are likely to be formed, and which molecules are less stable and less likely to be formed.

For example, H2 and O2 can form water, or they could form hydrogen peroxide, H2O2. You'll learn that H2O2 is not particularly stable, at least compared to water, and chances are if you react H2 with O2 you would form water. But why is H2O2 less stable? It's because the O-O bond is weak. Why is the O-O bond weak? There's no way you can answer this without at least some knowledge of MO theory. Why does MO theory work? Well, that's a problem for quantum mechanics.

So, ultimately, it is not about "first principles", which (IMO) in chemistry is basically equivalent to quantum mechanics. You could go that route, but it would be horribly complex, but more importantly it would require a great deal of knowledge that you do not have yet. Most of the time, we would rely on what we already know to predict the unknown. Also, please don't read McQuarrie, stick to gen chem textbooks.

You mentioned QM and statistical mechanics, which I am assuming you are trying to use to "build up" macroscopic systems from "first principles" - those are considered "advanced" topics because you do not need them to be able to develop chemical intuition about what goes on in big systems. The overall idea for chemistry is therefore: 1) Understand how macroscopic systems behave (stoichio, most of inorg and org, thermo). 2) Understand how small systems behave (QM). 3) Link the two (stat mech).

1 hour later…

1:19 PM

=^.^=

@orthocresol, that's too much text for Friday! :D

2

3 hours later…

4:21 PM

@Wildcat Here: 🐠🐠🐠

I was just bored since it was a period in between classes :D

Have a good weekend everybody (when it comes) :)

Martin - マーチン

It's been here for a while now... A beery while....

But yeah, you all shall have fantastic weekend, too.

Hm so, is the TRE maintained ?

4:55 PM

._.

1 hour later…

6:19 PM

Hello?

@Jan @orthocresol @Mithoron @Loong @Wildcat @ToddMinehardt you guys here?

I'm here

I was going to say "I am sorry for being late" but I am not even late!

@Mithoron do you want to do TRE?

@TanMath Strange, somehow forgot about it, we could do some retagging but seems there won't be real TRE

@Mithoron @ina is going to be angry... the previous TRE was supposed to be the last one for episode 1. Yet, since no one (except me) participated, @ina said that we will do a new one..

I am also angry at the community of Chem.SE (apart from you, thanks for showing up!)

No one should be angry lets ping some other guys

6:30 PM

@Mithoron ok... let's annoy them so that they regret not coming for the TRE! hehehe ;)

@AinzOoalGoal Want to do retag also @pH13

actuslly, gota quuickly go... I will BRB...

@Mithoron Sure

So lets edit a little one-taggers

Think we can use this old query: data.stackexchange.com/chemistry/query/368033/…

I am back.l.

So here is the deal: the tags are thermodynamics and acid-base...Can can think of any other tags?

6:37 PM

@user685252 Welcome to Periodic Table

@TanMath I'll check

You tell me how many tags you want to do... then I will tell you where to start and end in the query...

You do those tags, and you can ask for more!

@TanMath 30

@AinzOoalGoal so you go to the query, put in "acid-base", and start from:

7

Q: Why does ammonia act as an acid in only the first of these two reactions?

$$\ce{2Na(l) +2NH3 (g) ->2NaNH2(s) + H2(g)}$$ $$\ce{CH3Cl (alc) +NH3 (alc) -> CH3NH2 (alc) +HCl(alc)}$$ Doesn't ammonia donate a proton in both cases?

and go till:

3

Q: What makes protons give the property of acidity?

Bronsted Lowry definition of an acid says that an acid gives away protons. What I don't understand is what makes dissolved protons grant the property of acidity? Like, why would dissolved protons eat up materials? My question applies to bases too, I suppose. And I guess you could include Lewis-...

ok

I think this is 30 questions if I can count properly! remember that not all of them need to be retagged @AinzOoalGoal

6:42 PM

@TanMath Maybe 20 for me

@Mithoron ok... start from:

3

Q: The acidity of group 4 tetrahalides

I've been asked to compare the relative acidity of $\ce{CF4}$ and $\ce{SiF4}$. As both have noble gas structures neither can act as a lewis acid and so I assume the question is inferring that they are in solution. My guess is that under aqueous conditions they could react via some sort of hydro...

and go till:

2

Q: Thymol Blue - molar absorptivity

I did a lab about spectrophotometry and right now I need the molar absorptivity(ε) of thymol blue in acidic solution and also in basic solution. I have tried looking online but I haven't found the data I need. What is the molar absorptivity of thymol blue in acidic solution and in basic solution...

And just like I said to Ainz, not all of them need to be retagged...

Also, to both of you @AinzOoalGoal and @Mithoron try your best to do other substantial edits in the title or body as well...

@TanMath Ok

I will do some questions myself...

@Mithoron Thank you :-)

@Mithoron @AinzOoalGoal how is it going?

6:57 PM

@TanMath Fine :-)

almost done with your first round?

Ah, no :o 30 is quite a lot

@AinzOoalGoal it is fine... the TRE will be extended with 30 more min.

ok? might have time to do another round!

@SanchayanDutta Hello, we're doing a little retag

@TanMath :D

chemistry.stackexchange.com/questions/26303/… should I leave it as that ? I'm not sure if another tag would be useful

7:02 PM

@TanMath We won't do that much in three - I have limit of suggestions and we shouldn't leave too much unrevised.

@AinzOoalGoal leave it as is...

@Mithoron if we are quick we can do more... sometimes, it is best to leave unrevised anyway.. that is what @Jan and @ortho said before...

@TanMath I'm not (yet) but I can approve sets of edits/close questions every now and again.

@Jan i guess that is fine...

@Mithoron @AinzOoalGoal you guys done?

@TanMath I just finished :-)

I'm not, was was busy reviewing :(

7:12 PM

@AinzOoalGoal you are fast! you want more?

@Mithoron ok...

@TanMath 10 more :P

ok... start from:

1

Q: Order of lewis basic strength

My teacher told me that order of lewis basic strength is inversely proportional to electro negativity. Comparing between iodide ion and chloride ion, chloride ion is more electronegative than iodide ion therefore iodide ion should be more basic than chloride ion but the order is reverse that is c...

and end in:

1

Q: Kb of hydride anion

I can't find any data about the Kb value of the hydride anion except that it's huge. Does anyone know what it is, or how I can characterize it? I know I can use electrochemical means but the only reaction I find with hydride ion is this one: http://en.wikipedia.org/wiki/Hydride#Hydride_ion

@AinzOoalGoal have you started?

Don't forget that you can flag to close, too, guys.

(Used up my 20 edit reviews already. That was quick =O)

@Jan why should we flag to close? @ina once said that if you want a question closed, then don't retag it....

@TanMath Just reminding; there was the odd question where I thought *mi~ght as well close*

7:18 PM

@Jan which one?

@TanMath yes

@AinzOoalGoal ok.. i wasn't sure, be ause you didn't say anything...

how are you doing @Mithoron ? am i overwhelming you with suggested edits?

@TanMath Aaa, neverending queue! :D

@Mithoron Blame me :P all my edits need to be reviewed

@Mithoron I am sorry for all those suggested edits.. I have to earn a lot more rep to reach the point where I can do my own edits...

7:35 PM

The orbitals tag wiki needs editing

@orthocresol so? I am not the biggest orbital expert...

@TanMath It passed, too late.

@TanMath I'm not necessarily talking to you, I'm talking to everyone

"Contrary to misconception, the electron does not follow the surface of the orbital, but instead can be found anywhere within it (usually with a 90% probability, due to the Heisenberg uncertainty principle)." The 90% is a convention.. not due to HUP

@orthocresol true... but i am part of "everyone"

"An orbital is a theoretical stable standing waveform shape in which one or two electrons can be found orbiting the nucleus of an atom." implies Bohr model of the atom

I think I will spend time clearing that up instead.

7:38 PM

@orthocresol That sounds weird indeed O_o

@AinzOoalGoal "The energy state of an orbital is a natural number; 1, 2, 3, etc." is weirder. :/

@orthocresol that isn't true always...

@TanMath I can see what it is getting at, but it is poorly expressed. The quantum number $n$ of a hydrogenic orbital is limited to the natural numbers, and the energy of such an orbital is directly dependent on $n$.

$1/n^2$ to be precise.

@orthoseal yeah, that thing looks absolutely horrific

@Mithoron please finish your retagging... the TRE was supposed to end 10 min ago...

7:43 PM

@TanMath (btw I forgot to tell you, I've finished)

@Jan I sense a soft hyphen!

`(.•.)´

@AinzOoalGoal oh.. I figured.. do you want more? i wanted to finish acid-base...

@orthocresol Not sure if your senses are great or perfect ;)

I mean, we could add another 15 to 20 min...

@TanMath How many more are left ?

7:45 PM

@orthocresol what is this soft hyphen stuff?

Hm, my home hockey team has only been playing 34 min but is leading 7:0 \o/

A soft secret @TanHidden ;)

@AinzOoalGoal 27..

@TanSoftHyphen <-----

@orthocresol how do you do it?

@TanMath Ok, I'll do 15 :-) can you take care of the others ?

7:47 PM

@AinzOoalGoal sure!

let me get your questions..

@AinzOoalGoal start here:

0

Q: The Hygroscopic Nature of KOH

How does potassium hydroxide react with carbon dioxide? I heard that KOH absorbs carbon dioxide. What is the reaction, and what is the mechanism? Is this a Bronsted-Lowry acid/base reaction? A Lewis acid/base reaction? What is the reaction, and what exactly is it? After some consideration, I'...

and finish here:

0

Q: Hydrolysis of ammonium cloride

As we all know ammonium chloride is a acid. And what explains this is its salt hydrolysis. It breaks down into ammonium and chloride ions. Ammonium react with water to produce hydronium or hydrogen ions. But then why can't chlorine ions react with water to produce hydroxide ions? Is there any w...

@AinzOoalGoal you have started?

yes @TanMath (I answered before, but my connection keeps breaking :-( )

@AinzOoalGoal ok.. its ok.. I have about 5 more left...

Hey guys. I'm reviewing your tag edits and some of them are a bit dubious. Just because a question contains a word like 'equilibrium' or 'lewis' doesn't mean that it should automatically be tagged with equilibrium or lewis-structures. Please read the question carefully and only apply tags that are useful for finding the question.

3

@bon can you give examples?

There were a bunch of questions about Lewis acids/bases which were incorrectly tagged with lewis-structures.

8:01 PM

@bon weird.. If they talk about the lewis structure of a Lewis acid, then I include it.. like the sulfur trioxde one...

@bon might be me. There were one or two questions where I was unsure whether I should add it or not, since the OP didn't explicitly ask smthing about it in his question, but it seemed to me that it played a key role, and thus would be likely to be used as a keyword. There should only be one or two instances of that happening though

@TanMath Done

@AinzOoalGoal ok.. so we are waiting for @Mithoron ...

i'm done

@Mithoron great!

The longest TRE is over! We have finished all 117 of the acid-base (although not all of them was retagged)! Amazing accomplishment!

:P

Some of them are indeed barely retaggable, I've seen more than a few "why is base XX stronger than base YY ?" etc

8:10 PM

@AinzOoalGoal true... but those are really homework questions...

yeah, but it's not always clear

@TanMath I don't think it was longer than normally

@Mithoron no, it was almost 2 hours, wasn't it?

rather about 90 min.

You started pretty late, didn't you?

8:21 PM

hi all - apologies for missing the event,

8:0 =3

@Jan Good day to be a fan :D

Two more TREs and I'll get an edit reviewer badge =D

@orthocresol Oh yes =3

@Jan Very late - about two hours later

@orthocresol We just have to hope it stays something nil =3

8:27 PM

@Jan You have to give the opposition a bit of a chance otherwise it's not fun!

They're next to us in the ladder, so~ …

@Jan Oh, that changes everything...

Oh an opponent's player just got a match penalty D=

And there's goal number 9 =D

1 hour later…

9:47 PM

@bon Just so you know, I wasn't in this TRE.

@Ϻ.Λ.Ʀ. God not agin :((

reddit.com/r/news/rising

@AinzOoalGoal Wha?

See the top links (unrelated to the TRE)

I didn't say I won't be in the next one.

@AinzOoalGoal Oh. :(

10:09 PM

See ya, guys o/

@Jan \o

@TanMath +1,000,000,000,000

@Jan bye!

@Ϻ.Λ.Ʀ. hello!

@TanMath Hey!

10:25 PM

@Ϻ.Λ.Ʀ. so we looked through 117 questions but not all of them needed to be retagged... I hope I helped... For some reason. i am very passionate about the TRE...

@TanMath You helped greatly! Thanks for stepping up! (づ｡◕‿‿◕｡)づ

@Ϻ.Λ.Ʀ. unfortunately, for the next few TREs (possibly for the next two), I will not be able to make it unless the TRE is delayed by about half and hour or an entire hour... It seemed that delaying it by an hour didn't really affect us.. Mithoron was still there, and Jan was (kind of) there, along with bon (although Jan and bon only did the reviews)...Why have you put the time at 16:30 UTC?

@TanMath Because people were comfy about it. We can change the time anytime you want to any time you want.

@Ϻ.Λ.Ʀ. 17:30 UTC will be better for me.. You should ask the others if that is fine...

CHAT: Should the next TRE be at 17:30?

3

10:51 PM

@Ϻ.Λ.Ʀ. For me it rather the later the better

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The Periodic Table

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