The Periodic Table

Avnish Kabaj

00:43

@pentavalentcarbon In my defense I thought that the post would have been deleted way back

Secret

02:35

nature.com/articles/s41567-018-0103-2

No, you cannot use born Oppenheimer in molecules with many light atoms especially in phoroionisation

Tanner Swett

I thought of a pointless riddle a year or so back. Suppose you're in a world where, for whatever reason, fuels of biological origin are impossible to obtain. How can you make hydrocarbon fuels, such as gasoline?

I thought of one method that would probably work. I'm no chemistry expert, so maybe this wouldn't work at all, or maybe it's a hilariously inefficient way to solve the problem.

Heat calcium carbonate, or mix it with acid or something, to release carbon dioxide. Put the CO2 in a chamber along with magnesium and ignite it, producing carbon and some kind of magnesium oxide. Heat the magnesium oxide in a vacuum to turn it back into magnesium metal.

Well, gee, I just stumbled upon a bunch of Wikipedia articles with relevant information. Some keywords: methanation, synthetic fuel, the Sabatier reaction, and the Bergius process. None of these involve magnesium.

Secret

02:53

You will probably need a lot of carbonate to do that and carbonate by itself is no fuel

Not to mention I will imagine the heat input to thermo decompose MgCO3 may outweigh the heat output or something

I think I might need to call this carefully using a Hess diagram to be sure...

Calc*

Tanner Swett

Oh, for some reason it didn't occur to me that burning Mg in CO2 might produce MgCO3 instead of MgO.

Secret

04:40

Magnesium is quite reactive, it can react in both N2 and CO2

Secret

sciencedaily.com/releases/2018/04/180417115711.htm

More CO2 fuel conversion efforts

pubs.acs.org/doi/10.1021/acs.chemmater.7b05015

Heat transports faster when MOFs are interpenetrated

sciencedaily.com/releases/2018/04/180417115651.htm

Hmm... I wonder if that will mean Tungsten is potentially more toxic than mercury since it does not get removed if the dose is low

Gaurang Tandon

05:45

-yesterday seems to have been one of the busiest days in this room-

Gaurang Tandon

05:56

@pentavalentcarbon That's why this was a comment and not an answer. Anyway, thank you for making it more useful. — Ivan Neretin 11 hours ago

to be honest, it would have taken him only a minute more to make his initial comment a bit more useful

if he's spending his energy writing a comment in the first place, why doesn't he not spend 10% more energy and make the original comment twice as more useful?

beats me

and it makes me a bit sad when new users reply to him asking for clarification. they don't know that his reply won't be more than a single line, and that they would spiral into a back and forth discussion, confusing the OP further at every stage...

Gaurang Tandon

06:36

0

A: Hidden points of editing you probably didn't know

Vary font sizes within your post Quoting from the very well-written Hypertext Help with LaTeX The following type size commands, in order of increasing font size, are supported by LaTeX. \tiny \scriptsize \footnotesize \small \normalsize (default) \large \Large (capital "L...

my final typeset doesn't work, any $\LaTeX$ pros please help

-----------
Ah, a fresh new round of enlightening with [tag:homework] awaits them :P

9

Q: Homework questions, and what to do about them

Well, a new problem is upon us: the homework question. The first has been posted on our site. What should our policy be for homework questions?

actually this cs.SE post is pretty good

10

A: Homework policy

Policy We do not try to decide which questions are homework, and we don't use a special tag. Users that want to receive hints rather than full answers should say so, and answerers should honor such requests (by not posting details or hiding them in spoiler tags). Other than that, the usual quali...

Gaurang Tandon

07:00

useful reading

15

Q: How to treat a "please do my homework for me" question?

I see questions like this every so often, usually the poster doesn't just copy and paste the text directly from their assignment, but one did as How to find ring of coverage of GPS Satellite on WGS-84 ellipsoid?. None of the flag categories really fit, but I think it should be removed, if only t...

discussion scope

Gaurang Tandon

07:11

this should be made into a canned response -

17

A: Bringing on board new diamond moderators?

We (the moderators) haven't really discussed requesting a new moderator from the Community Managers. We know that it's an option... and if the users feel like the moderation of the site is somewhat lacking, we're happy to consider your point of view on the subject but, as of right now, we don't t...

(i'll stop now)

Abcd

08:40

0

A: Calculation of the pH of a mixture of a strong acid and weak acid

-The above workup should be pretty easy to understand. -The only tough task is to understand the approximation in 3rd last step.

@GaurangTandon I don't get how this answer contributes anything new.

Martin - マーチン

down-vote and move on

Gaurang Tandon

08:55

@Martin-マーチン I disagree with "move on". This is the poster's second answer of his entire lifetime, and even though the answer is out of place, it is still complete, comprehensible and the poster has shown effort in solving it. we can at least be a bit more polite in telling them their mistake.

Martin - マーチン

sorry, but I have long passed the point of caring for things like that

Gaurang Tandon

well, the poster in question in question isn't a 1-rep user with a generic user11220055 name.

never mind though

user280247

12:35

Hi, maybe you can help with a definition. As far as I understand, a substance can be defined as any compound or element, which can't be separated by physical processes.

user280247

Then air, although it is an homogeneous phase and has definite properties as a salt crystal (for example), is not a substance, cause air can be separated by phys. methods.

user280247

Do you agree/like the definition?

pentavalentcarbon

13:09

@GaurangTandon \footnotesizeisn't in docs.mathjax.org/en/latest/tex.html presumably because it has "footnote" is the name, meaning it shouldn't be needed for math

@GaurangTandon I haven't seen it get that bad, but you just can't worry about it so much or you end up like me. View every question as a fresh start.

JavaScriptCoder

13:30

:P My science olympiad stuff is in 1.5 days, and I'm seriously concerned (I'm on the things i know the most about, materials science and chemistry). Someone help me destress

Two front/back pages of 10 pt font is all I have

AAAAAAAAAAAHHHHHH

Gaurang Tandon

14:52

@pentavalentcarbon hmm right

@pentavalentcarbon oh, well, alright

@santimirandarp I think I agree, but I'm not the best person to answer this

@JavaScriptCoder just skip it, it's too late ;)

Gaurang Tandon

15:07

@orthocresol I may be wrong but... I think taking the books down would be too excessive a measure from our side. I agree with you when you say that the formatting is excessively poor, and the content is hardly useful, but then, it's upto the publisher (and not us), to decide how the content gets published. As long as it's legal, we shouldn't worry.

There are probably many other people and bots crawling our site, especially in malicious ways we aren't aware of. The point is, if the publisher has politely given us the power to suggest changes to his book, I think it's best if we do it moderately. An extreme measure, like taking the books down, appear as excessive intrusion, at least to me.

I understand that you're worried about the content being wrong (especially with Uncles answers) and that could give the readers a false impression of what great content our site has.

Apoorv Potnis

5

Q: Glowing stone - Scarab carving

I have an intriquing question and, after searching whole Google, found almost no information. I simply don't know where else to look for answer and so I am asking you. When I was a child, my parents travelled with me to Egypt and there, they bought me a little scarab beetle carved of some stone,...

minerals

Does this belong to Earth Science.SE?

Gaurang Tandon

(continued) But, that problem is simply solved by adding a big disclaimer in the About section of the book : "the answers have not been manually verified from experts in chemistry universities or from the Chem.SE users. The publisher nor the Chem.SE users are not responsible for any factual inaccuracies." thoughts @orthocresol?

Apoorv Potnis

Or has more chance of being answered there?

Gaurang Tandon

@ApoorvPotnis hmm, would you mind asking them in their chat room if it's on topic?

I think I agree with you, but just to be sure

JavaScriptCoder

15:25

@GaurangTandon its too late TO PULL OUT!!! (running waving arms)

JavaScriptCoder

15:47

@orthocresol

"Antarctica has dry valleys where, for some reasons, seals sometimes went. It is a bad place for seals, and they died. It is a bad place for microbes and everything else too, so the dead seals did not decompose. These mummies are hundreds of years old."

orthocresol

16:37

@GaurangTandon I don't think it's extreme in any way.

Abcd

@JavaScriptCoder ortho can even change his username to "orthocreseal" (if he is a seal-fan)

Anonymous

Puns everywhere

Gaurang Tandon

@orthocresol it isn't extreme? Okay then, that voids my argument.

I still find it extreme though - taking down a book that someone took their time to curate (howsoever poor, but an effort nonetheless). But if you don't, no issues.

JavaScriptCoder

@Abcd :)

orthocresol

@GaurangTandon This is a matter of opinion more than fact. If you think it's excessive, then we just need to agree to disagree

That's perfectly fine, and that's why there are voting buttons on meta

Gaurang Tandon

17:01

Yep, exactly, agreed.

Though I'll probably update my answer to add in a bit about not taking down the book, I hope that's OK

(there are six votes already, though if the voters disagree, I think they'll just change their votes)

(I'll push an edit later tomorrow)

Though I definitely didn't want that factual summary to gain 8 votes :P

orthocresol

I won't downvote your post, anyway. Downvotes on meta indicate disagreement but it doesn't make sense to count downvotes on posts because the same person can upvote one post and downvote another

Hence, we just go by the number of upvotes.

Gaurang Tandon

Ah, fair point. I didn't think of that before. But it's good

Ah, fair point. I didn't think of that before. It is good. I downvoted your post though, only to signal disagreement. But, now, I feel you are absolutely right. Downvotes are not effective in these cases. Okay, I am sorry, I wish to retract it now :(

orthocresol

17:17

It doesn't matter, I don't feel hurt

2

It's perfectly fair to downvote something you don't agree with, it's just that when trying to determine the community consensus we don't count it

Gaurang Tandon

Thank you :-) though I'll retract it as soon as you edit it. downvotes are not constructive in such cases. I definitely understood that point now :-D

Avnish Kabaj

Making it to HNQ is like lottery

Gaurang Tandon

You meant HMP? Hot meta post?

Avnish Kabaj

12

A: Why does potassium react more violently with water than lithium?

For the reaction, $$\ce{M -> M+ + e-}$$ the heat liberated is highest for lithium owing to its high negative $E^\circ$ value so one would think that the reaction must be most vigorous. The reason behind the more violent reactivity of potassium rather than lithium lies in kinetics and not i...

This one

Made it

Gaurang Tandon

Well, the mod can always put a featured tag, which makes me wonder why ortho didn't do it already. @orthocresol you may wish to add a featured tag, favorably after I make the final edit to my answer. Could you?

@AvnishKabaj ha, then you did not see this lottery instead

52

Q: Do there exist pairs of distinct real numbers whose arithmetic, geometric and harmonic means are all integers?

I self-realized an interesting property today that all numbers $(a,b)$ belonging to the infinite set $$\{(a,b): a=(2l+1)^2, b=(2k+1)^2;\ l,k \in N;\ l,k\geq1\}$$ have their AM and GM both integers. Now I wonder if there exist distinct real numbers $(a,b)$ such that their arithmetic mean, geometr...

algebra-precalculus means

I'm gonna flush all that fresh rep down into bounties anyway. The answers I got there were very very brilliant.

Avnish Kabaj

17:27

Holy moly Gaurang

52

Gaurang Tandon

Hehe

M.A.R. ಠ_ಠ

18:30

Ugh, @Gau's being nice again

SNAP OUT OF IT

Mithoron

@GaurangTandon HNQ making, shame on you

@M.A.R.ಠ_ಠ o/

M.A.R. ಠ_ಠ

@Mithoron {o

I have a thick elbow

Mithoron

o.O

:D

M.A.R. ಠ_ಠ

@Mithoron you're really easy to annoy

965

Q: Visually stunning math concepts which are easy to explain

Since I'm not that good at (as I like to call it) 'die-hard-mathematics', I've always liked concepts like the golden ratio or the dragon curve, which are easy to understand and explain, but are mathematically beautiful at the same time. Do you know of any other concepts like these?

soft-question education big-list visualization

Wait, I'm annoyed too now

WHAT THE EFFING EFF IS THAT EFFING QUESTION DOING AS THE TOP EFFING QUESTION OF THE EFFING SITE

Now I feel better

Mithoron

Heh, twas half-serious ^^

M.A.R. ಠ_ಠ

18:37

965 votes. Goddamnit

Mithoron

:D

There, there X)

M.A.R. ಠ_ಠ

Now consider the fact that that's the score

It has probably 1100 upvotes or something

Mithoron

Probably not even 1000. Downvotes are terribly rare

Mithoron

19:01

@M.A.R.ಠ_ಠ Are all new user all upvote, upvote no critic, nice nice?

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