The Periodic Table - 2016-05-09

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Martin - マーチン

12:55 AM

@Jan Now the last statement of my progress-monitor does not really match the question any more, does it. Re: meta.chemistry.stackexchange.com/q/2815/4945

@Jan Re: meta.chemistry.stackexchange.com/q/3218/4945 I closed that quickly to get that bug report dealt with - If the devs see that it is closed they don't need to bother. They have more pressing matters to attend to.

2 hours later…

2:53 AM

@Martin-マーチン Thanks for cleaning up that post! It does look much nicer

Martin - マーチン

no problemo ;)

I'll be sure to use the align command in the future

Martin - マーチン

well derived

I don't know where all you guys learned how to use these tables and alignment commands

Martin - マーチン

haha... yeah learning by doing...

2:54 AM

Learn by copying for me

Martin - マーチン

i wrote my phd thesis in latex... you lern stuff

WOW

Martin - マーチン

most of it is pretty useless knowledge after that ;)

but i like tex, it has some unmatched elegance to it

also... found something cool today :D

in MathJax/(La/Xe)TeX help, 2 hours ago, by Martin - マーチン

0

A: A new Formatting Sandbox — please test stuff here

$\require{begingroup}\begingroup$ Holy Moly... automagic references... magic $\rm\LaTeX$ style The equilibrium constant is defined by the expression $$K_x=\prod_{\ce{B}} x_{\ce{B}}^{\nu_{\ce{B}}}.\tag1\label{equ-constant}$$ $$K_x=\prod_{\ce{B}} x_{\ce{B}}^{\nu_{\ce{B}}}.\tag1\label{equ-consta...

NO MORE MAGIC

Martin - マーチン

!!flip/magic

2:56 AM

(づ๑ʖ๑)┛︵ɯɐƃᴉɔ

Wowowow

Maybe I should go back and number my equations

What beautiful sorecery

Martin - マーチン

3:08 AM

haha... yeah... high level wizardry...

harry couldn't do better ;)

Martin, I'm having a problem

\tag10\label{...} is giving

[equation]0 (1)

Fixed: \tag{10}\label{...}

Martin - マーチン

yes... in general for any latex command that does not switch globally you need to encase the argument with braces

@Martin-マーチン chemistry.stackexchange.com/questions/50880/…

!!!!!!!!!

Such beauty!

Thank you so much!

Martin - マーチン

3:23 AM

indeed... looking good ;)

i like the hyperlink thingy, too

2 hours later…

user116211

5:13 AM

Mart can go!

user116211

Rare picture!!

user116211

user image

5:43 AM

How about this, guys:

> I have had a request for solid information about this on Chemguide since 2002, during which time this page will have been read by hundreds of thousands, if not millions, of visitors. In all that time, nobody has suggested an explanation which would account for the low melting point value for magnesium, or the lack of any pattern with the other two properties.

> If you can see flaws in what I have said above, please get in touch with me. I would also be grateful to anyone who could point me towards an explanation, even if it is too difficult to use at this level, or even too difficult for me to understand. But that explanation has to be capable of accounting for all the variations in the data.

Chemguide - "Atomic and physical properties of Periodic Table Group 2"

and you want to do it?

@manshu I just wondered if there's a question on Chem SE discussing this

> There is one book that I have come across which is honest enough to admit the difficulty. A.G.Sharpe, in his degree level book Inorganic Chemistry admits that there is no easy explanation for the variations in the physical data in Group 2. If that is indeed the case, as looks pretty likely, it is a pity that anyone should encourage faulty explanations like the one above. Much better to have no explanation than a deeply flawed one.

4

Q: Why does magnesium have the lowest melting point of all earth alkalis?

Why does magnesium have the lowest melting point of all earth alkali metals?

4

Q: Why does magnesium have an exceptionally low melting point?

Why does magnesium have a lower melting point than both calcium and beryllium? It does not seem to fit into the group trend.

inorganic-chemistry metal melting-point

use the second link

it has an answer.

But I am feeling too lazy to read it.

This website seems to make a good argument that the cause of magnesium's low melting point is not understood (see the "Trends in Melting Point, Boiling Point, and Atomisation Energy" section). The page also discusses why the reasons typically advanced probably aren't valid. — ron Mar 10 '15 at 17:29

@manshu Thank you!

It has something to do with crystal structure. I see. I won't upvote it, because I don't understand it much.

I wonder why Be reacts with NaOH, and Mg does not.

've just found a whole page about this

Martin - マーチン

6:01 AM

@MAFIA36790 reboot ;)

6:19 AM

> Beryllium chloride is known as an electron-deficient compound because it has the two empty orbitals at the bonding level.

I'm not sure what this means

Be has three unfilled p-orbitals

Ah. Two unfilled p orbitals

> "Electron deficiency occurs when a compound has too few valence electrons for the connections between atoms to be described as covalent bonds." (Wikipedia)

a hazy definition

Martin - マーチン

In beryllium chloride beryllium forms two bonds and therefore shares four electrons. It therefore must partake in two molecular orbitals, hence two orbitals remain unoccupied. Since p orbitals are higher in energy, it will be mostly these.

7:02 AM

nods

user image

I wonder if they are "replaced" by water molecules from the environment, or it is just that H+ connects to the OH- groups in the coordination compound

7:24 AM

Why (do?) more active metals react with water to form hydroxides, and less active metals react with it to form oxides?

Active metals have low electronegativity, high atomic radius.

Less active, like Zn, have mid-level electronegativity, smaller radius.

Does that somehow affect their reactions with water?

(goes to google)

Okay, feel free to downvote. I need a reminder of why this is so.

0

Q: Why do metals react with water differently?

Active metals like potassium and calcium produce hydroxides when put into water, while less active metals, like zinc, produce oxides. Why is it so?

metal hydrolysis

(0:

1 hour later…

8:47 AM

@All, I will be AFK for about 20 days because of final exams., starting on May 13th.

AFK? Acidic Fluoride Potassium?

ah.. away from keyboard. that's good. I hope you get 100% on the exam.

or "in the exam"?

Around the exam

Towards the exam

Never mind, just get to learning! I'll keep my fingers crossed

In Russian, "keep my fists clenched"

Russians . . .

It's a strange expression, I know..

user116211

9:09 AM

@PhMgBr Ah! ATB ;)

9:39 AM

@Martin-マーチン I don’t see too much of a problem, tbh. Yeah, I can write a blurb for the excerpt. Maybe the Wiki, too …

10

Q: What is the molecularity of a reversible reaction?

I know that the definition of molecularity of a reaction is number of species reacting in an elementary step. But considering the theory of microscopic reversibility for elementary reactions, each reaction can be assumed to be reversible. In that case, if $$\ce{A <=> B + C}$$ then what is the mol...

reaction kinetics

@MAFIA36790 Active Time Battle?

@Jan Astonishing t-Butyl

2 hours later…

user116211

11:28 AM

!!flip/All The Best

( つ•̀ω•́)つɐꞁꞁ ʇɥǝ qǝsʇ

1 hour later…

12:58 PM

@Mart I hope you are fine with my tag wiki edit =3

!!doubleflip/work

ʞɹoʍ︵╰(゜Д゜)╯︵ʍoɹʞ

Martin - マーチン

@Jan [tag:alcohols] doesn't work in excerpts O.o

but who cares...

1:26 PM

I don't get one thing: why (do?) we need the salt bridge.

I guess we're using a strong acid\strong base combintaion (KNO3) with purpose.

Ah, found three questions on SE about that.

2:04 PM

If we will just blow hydrogen through porous platinum, will hydrogen also be leaving electrons on the platinum and forming H+ protons?

Or does it do so only because the platinum is in contact with acidified water?

@CowperKettle If you blow hydrogen through porous platinum, you can build Döbereiner's lighter.

Döbereiner's lamp

Döbereiner's lamp, also called a "tinderbox" ("Feuerzeug"), is a lighter invented in 1823 by the German chemist Johann Wolfgang Döbereiner, the lighter is based on the Fürstenberger lighter and was in production until ca. 1880. In the jar, similar to the Kipp's apparatus, zinc metal reacts with dilute sulfuric acid to produce hydrogen gas. When a valve is opened, a jet of hydrogen is released onto a platinum sponge. The sponge catalyzes reaction with atmospheric oxygen, which heats the catalyst and ignites the hydrogen, producing a gentle flame. It was commercialized for lighting fires and pipes...

> the lighter is based on the Fürstenberger lighter

Oh, that explains a lot.

> When a valve is opened, a jet of hydrogen is released onto a platinum sponge. The sponge catalyzes reaction with atmospheric oxygen, which heats the catalyst and ignites the hydrogen, producing a gentle flame.

Does it make hydrogen give away electrons, I wonder.

The flame is quite weak, on YouTube

The catalytic combustion of hydrogen over platinum (Döbereiner's lamp)

Cool to have one.

Wikipedia says:

> The choice of platinum for the hydrogen electrode is due to several factors:
inertness of platinum (it does not corrode)
the capability of platinum to catalyze the reaction of proton reduction

"proton reduction"? But we create protons by blowing the hydrogen through it. Isn't it an error?

O_o

proton reduction should create wholesale hydrogen out of a stream of H+

2:22 PM

@CowperKettle where did you find that?

@Loong %**here**, on Wikipedia

ok, so that does not refer to the lighter.

no, that's about the standard hydrogen electrode

From an answer on SE:

> As for why this happens, it has to do with how platinum metal binds to hydrogen atoms. Hydrogen gas (H2) adsorbs ("sticks") to platinum metal, which causes the H-H bond to break as two H-Pt bonds form. This makes it easier to remove an electron from each H atom, generating two H+ from H2. The thing that makes platinum such a good catalyst for this process is that it binds hydrogen gas strongly enough, but not too strongly.

So after all we generate H+. This seems to contradict what Wikipedia says.

In the lighter, platinum catalyzes the reaction of H2 to H+ (or H2O). However, often a heterogeneous catalyst can also catalyze the reverse reaction of an equilibrium (if forward and reverse reaction follow a similar reaction pathway).

2:58 PM

Okay, now I've read about electrochemical series. Zn is below Na in the series, but does that explain why it forms oxides?

user image

I wonder why this line is bolded in the series

If we bubble hydrogen gas through a basic solution, it will give away electrons and form water?

1

Q: Why does sodium react with water to produce a hydroxide, while zinc produces an oxide?

Sodium belongs to the so-called active metals and produces a hydroxide on contact with water. Zinc produces an oxide. Why is it so? I was given a hint: to read up about electrochemical series. I've read about it, and naturally zinc is below sodium in the series. Zinc is slightly below this bo...

metal hydrolysis

A reworded question.

3:27 PM

@CowperKettle " I do not fully understan" d

@Hippalectryon Thanks!

I found a page that might help

But before I read it, someone might post an answer anyway.

Or, read it and answer your own question :-)

4:04 PM

To all reviewers: this is an attempt at an answer. Just because it is wrong doesn't mean it should be deleted. Downvote it instead. — bon 25 mins ago

@bon by the way, the review was completed by your vote (Looks OK); the post is no longer in the low quality review queue.

2 hours later…

6:24 PM

@orthocresol ¿Y también necesitamos "the s-block", no?

@Brian 不明白

@orthocresol Mandarin?

6:49 PM

user image

Good evening all! What's the meaning of this equation, I wonder. Oxygen is bubbled through water and receives 4 electrons?

The reaction is tilted to the right?

Because the electromotive force is positive?

Dobry vecher, @DeNiSkA! Welcome back.

:D

Bye, Ortho.

@CowperKettle This is a half-cell reaction

@Brian 是的，这就是华语

Specifically, a reduction reaction, where, as you say, oxygen is taking up electrons.

6:55 PM

I first read about such reactions today, relative to the standard hydrogen electrode.

In the real world, it would have to be paired with an oxidation reaction, as the source of the electrons.

nods

@orthocresol Yaaaah, I took 日本語 for 3+ years, but have no grasp of Chinese at all.

It is paired. I was just checking whether I understood it right.

@CowperKettle Yup.

6:56 PM

@Brian You learned Chinese for 3 years? O_o

The $E^\circ$ indicates the "standard reduction potential"

No, no - Japanese

ah

I remember ... ][ this much, at least off the top of my head.

I really wish Duolingo had a Japanese module, I would totally be using it.

@Brian Japanese is more fun imo. I grew up speaking Chinese and English. Yes about Duolingo, totally...

I was just reading books in English and rote-learning words..

6:57 PM

I self-studied Japanese for a while, enough to construct some basic sentences, but that was a few years ago and I've forgotten nearly everything..

@orthocresol I really enjoyed the language a lot. Esp @ MIT; the three Japanese ladies who teach it there are really excellent.

3 years is a long time actually, you must be pretty decent at it

Anyways, standard reduction potentials are set by reference to the reduction of protons to H2, which is defined as 0 V.

I know - I read that today on Chemguide. (0:

@orthocresol I was pretty good, I think -- really weak on vocab and not so strong on-the-fly speaking, though

@CowperKettle Ok... should I stop now? :-)

7:00 PM

@Brian By all means, no.

@Brian Speaking is really really hard!

@ortho I've always said I was backwards from native speakers -- I knew the grammar really well, but was lacking in basic vocab

"air"

"cow"

gyu?

Whereas kids learn a lot of basic words first, and then back-fill the grammar details

which proves that learning grammar is the last thing you should do

7:01 PM

<nod>

wife and I are starting our boys on Spanish early -- trying to exploit that young-child magic-language-brain thing

NO MORE MAGIC

..

Mmmhm, I have no idea how kids do it so well...

@CowperKettle So, anyways, re reductions -- a positive SRP means the reaction is more favorable compared to proton reduction

negative means less favorable

@orthocresol neurogenesis

(at equilibrium, at least -- as the current goes up, things tend to go cuckoo)

7:03 PM

nods

@orthocresol @CowperK Yep - their brains are just wired to internalize that sort of thing.

Adult neurogenesis is faster in young persons.

@CowperKettle I think that's about it... any further questions?

@Brian Thank you! No questions yet. (back to reading)

Yup yup!

7:06 PM

in an effort to better connect with our user base here at chem.SE, I think I should learn German

3

vielleicht

@orthocresol <nod>, I'm trying to do Spanish and German double-barreled on Duolingo currently

It's... kind of a lot.

@Brian That's really ambitious

@orthocresol It's not been as intense as I feared, though.

Just time-consuming.

I actually did the first 1 or 2 lessons on German just to try it out

Then I found out there was no Japanese, so I stopped.

7:08 PM

Some of the early sentences are kind of funny.

I've heard

But never actually seen them since I never got past "Ich bin ein Junge" :P

The cognitive dissonance of an "Ich bin eine Frau" is ... interesting.

:D

because of the neuter gender?

Spanish, too: "Mis faldas son blancas." O.o

7:11 PM

nothing wrong with crossdressing..

> Conducted by professors at City University of New York and the University of South Carolina, the study estimated that 34 hours on Duolingo may yield reading and writing ability of a US first-year beginners' course university semester, which takes in the order of 130+ hours.

It is really that good?

@CowperKettle Oy, that too. Das die der den einen Wahnsinn.

7:26 PM

@Martin-マーチン Okay, I tried O:)

8:02 PM

user image

As I understand, we can also obtain NO3 to NO2 reduction, not to NO.

In some Russian examples, Cu + HNO3 >> Cu(NO2)3 + NO2 + H2O

Maybe if HNO3 is in overabundance, it only reduces to NO2

And if there's enough Cu, then it reduces all the way to NO

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Transcript for

May '169

The Periodic Table

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