The Periodic Table

Jan

00:02

You know how the name Elschenbroich immediately makes me want to mimic a thick Cologne or Düsseldorf accent?

Loong

You still know Elschenbroich? I made some nice bisbenzene vanadium crystals for him as a student.

Jan

The person? No. But the name screams Niederrhein.

Loong

(Actually, I simply forgot the solution for a week, so the crystals became huge.)

orthocresol

Huge crystals = best crystals

Jan

(That’s okay. In the Klüfers group, I was writing up the report of my research project, came back a few weeks later and the PhD student supervising me said ‘yeah, by the way, you doubled your crystal structure yields. You left a flask in the fridge which happened to crystallise by accident.’)

Loong

00:07

@orthocresol Yes, the crystals were so large, the Elschenbroich group sent them in for neutron diffraction.

@Jan Heh, just like that. Furthermore, the raw solution of my bisbenzene vanadium was almost black; so you couldn't see the crystals before filtration.

Jan

I’m trying to remember whether there was anything I still wanted to do today except going to bed.

gannex

hmmm elschenbroich is actually not that expensive in English. I thought it would be like Holleman-Wiberg, but no. Maybe I will buy one. My prof is incredibly French and he tells everyone to use a combination of Didier Astruc and Yves Jean's books, though.

orthocresol

The university library here has dozens of copies of Elschenbroich, but only one of Holleman-Wiberg.

gannex

I just checked. We have 0. I want to see why it costs so much!

But yeah Elschenbroich just has a little table, like Crabtree. I would like to find a book with a big table with hundreds of complexes.

I was wondering about [Fe(CO)4]2-. The frequency must be extremely low.

orthocresol

00:28

$1756~\mathrm{cm^{-1}}$

Jan

!!doi/10.1021/om00034a077

Chemobot

DOI 10.1021/om00034a077 :
"Methyl transfer reactions to tetracarbonylferrate(2-): rate and mechanistic studies"
First author : Ping Wang

Jan

:D Lol @ first author.

@Chemobot @Hipp: Please, no space between First author and the colon. We’re not french ;) Same for between DOI and colon. Also, a link would be cool ;) I would assume journal and citation to be more difficult, though. feature-request

orthocresol

I think a long time ago he was experimenting with putting the link, but it didn't work in multi-line comments.

If I remember correctly.

Jan

Well lets try this out
[To see if a link works in multiline comments.](http://pubs.acs.org/doi/pdf/10.1021/om00034a077)

Obviously, it doesn’t.

orthocresol

00:34

Maybe someone should feature-request that on meta.SE

Jan

(Then again, nothing’s restricting @chemobot from posting two messages, so …)

The complete opposite, actually. I paused before submitting because when I re-read it I sounded like a communist. — kingledion yesterday

Comments that are just fun to read =D

Ramanujan

01:37

!!test

Chemobot

edited !

Ramanujan

!!coffee

!!flip/Martin - マーチン

Chemobot

◟(`ﮧ´ ◟ )Wɐɹʇᴉu - マーチン

Melanie Shebel

03:41

Anyone have a better title than "Sulfuric acid electrolysis"?

3

Q: Sulfuric acid electrolysis

If I have aqueous sulfuric acid solution as electrolyte and the anode electrode is made out of copper and the cathode electrode is made out of graphite, what are the two reactions at the respective electrodes and why? Anode: $$\ce{Cu → Cu^{2+} + 2e-}$$ Cathode: $$\ce{2e- + 2H+ → H2(g)}$$ Total...

Also would anyone be willing to do a major cleanup on this one? It's a fairly popular unanswered question, but the question could use a bit of work:

2

Q: Relation between Specific Conductance and Equivalent Conductance

I have a question about the derivation of the formula for relation between Specific Conductance and Equivalent Conductance i.e. Eq. Conductance = k.V where, k= Specific Conductance ,V=Volume in ml Given link explains the derivation http://www.adichemistry.com/physical...chemistry.html (Check u...

conductivity

Bounty Hunter

05:29

51

Q: Why is absolute zero unattainable?

We were dealing with the Third Law of Thermodynamics in class, and my teacher mentioned something that we found quite fascinating: It is physically impossible to attain a temperature of zero kelvin (absolute zero). When we pressed him for the rationale behind that, he asked us to take a l...

thermodynamics temperature

Martin - マーチン

05:54

@Ramanujan Extended testing in chat.stackexchange.com/rooms/38172/chemobot please :D

@Jan Noooooooo! ;)

DOI http://dx.doi.org/10.1021/om00034a077
"Methyl transfer reactions to tetracarbonylferrate(2-): rate and mechanistic studies"
First author: Ping Wang

awww carp.... now it cuts-off the doi

@MelanieShebel that post is painful

Melanie Shebel

06:19

It hurts my body.

@Martin-マーチン Are we doing Winter Bash?

Martin - マーチン

o/ I very much think so... unless someone comes forward and presents good reasons, why chem.se should not participate :D

@MelanieShebel I don't think there is much to salvage there, the link points into Nirvana and the question itself, well..., errr..., I don't understand what it asks O.o

Melanie Shebel

Lame. It's a fairly popular question (no clue why.P

Martin - マーチン

some questions accumulate a ton of views just because they have the right trigger words

after all, this one is 2 years old

Melanie Shebel

Yeah, that's what I was thinking.

Martin - マーチン

06:34

I would guess, that this is a topic in one of the Indian standard tests... so quite a lot of people probably search for it

I just downvoted it, you might want to consider doing the same

Melanie Shebel

physicsforums.com/threads/…

Made the same day as the OP

MartianCactus

hey

so in the molecule CO2, carbon has a valency of 4 and Oxygen has a valency of 2 right?

Martin - マーチン

@MelanieShebel already left a comment on the q

MartianCactus

so the carbon forms 2 covalent bonds with each oxygen making a total of 4 covalent bonds and thus satisfying the valency of each atom right?

but what about CO?

there is only 1 oxygen in this case, then how can the valency be satisfied?

Martin - マーチン

valency is a pretty undefined concept

MartianCactus

06:48

hm...

like, the octet of both of them has 8 electrons..

Martin - マーチン

according to the qoldbook definition iirc, it is only defined for elements, so the valency of carbon is always 4

goldbook.iupac.org/V06588.html

MartianCactus

well..in CO2 the octet of both oxygen and carbon are completed right?

but that cannot happen in the case of CO

then why is CO formed?

and what is the charge of CO?

Carbon Monoxide i am talking about

Martin - マーチン

CO is a very complicated molecule with a very complicated bonding situation

20

Q: How can the dipole moment of carbon monoxide be rationalised by molecular orbital theory?

Despite the fact that oxygen is much more electronegative than carbon, the bond in $\ce{CO}$ presents a weak dipole moment. This observation can easily be explained using the concept of "dative bond", that is, one bond is formed with two electrons from oxygen, producing a polarization $\ce{O\bond{->

bond theoretical-chemistry molecular-orbital-theory

MartianCactus

how is it complicated?

all i see is a carbon, an oxygen and a double bond between them which doesnt complete carbon's octet

what is the charge of CO?

Martin - マーチン

well... for a start, there is not a double bond

7

Q: Why is CO practically nonpolar?

This question was in my book. According to me CO should be polar as it should have a dipole moment. But I found that the $\sigma$-electron drift from C to O is almost nullified by the $\pi$-electron drift from O to C. What is about the $\pi$-electron drift towards the Carbon atom? In Google it...

physical-chemistry theoretical-chemistry dipole

you really need to accept, that CO is one of the most complicated molecules there is. It defies any easy models...

MartianCactus

06:57

oh

so i can only understand it when I study higher stuff, right?

Martin - マーチン

have you studied resonance?

MartianCactus

the model they tell us about how every atom strives to complete their octet and makes bonds accordingly is partially wrong right?

what i understand is...

every atom wants to be in the lowest energy state possible

and the lowest state, most of the time, can be achieved through 8 electrons in the valence shell

Martin - マーチン

well, the octett rule is a very good guideline and it helps for period 2, and sometimes even for period 3

after that it gets a bit fuzzy

MartianCactus

but sometimes, the lowest state is something else which is why CO behaves the way id does..

but arent C and O both a part of period 2?

Martin - マーチン

yes

MartianCactus

07:01

so am i right on what i said?

sometimes the lowest energy state cannot be accomplished with 8 electrons?

and so atoms behave differently

which is why molecules like CO end up forming

Martin - マーチン

with a triple bond and a formal positive charge at O and a formal negative charge at C the octet is filled for both

MartianCactus

where the octet is not complete but the energy state is lowest..

oh

there is a triple bond?

in CO?

Martin - マーチン

well not exactly, but yes, in a first order approximation, this comes closest to the truth !!wiki/carbon monoxide

Chemobot

Carbon monoxide

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air. It is toxic to hemoglobic animals (including humans) when encountered in concentrations above about 35 ppm, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions. In the atmosphere, it is spatially variable and short lived, having a role in the formation of ground-level ozone. Carbon monoxide consists of one carbon atom and one oxygen atom, connected by a triple bond that consists of two covalent bonds as well as one...

MartianCactus

what comes closest to the truth?

am i correct on what i said about the "lowest energy state" stuff?

Martin - マーチン

07:05

3 mins ago, by Martin - マーチン

with a triple bond and a formal positive charge at O and a formal negative charge at C the octet is filled for both

MartianCactus

oh

Martin - マーチン

@MartianCactus yes, in principle. Every system tries to be in it's lowest energy/ most stable configuration - sometimes the "rules" to accomplish that are not quite obvious and you might need a firm grasp of higher concepts

MartianCactus

oh, ok

Martin - マーチン

you'll learn more when you advance in your studies

just keep an open mind about it and don't take everything you learn for the ultimate truth

it gets really exciting when the easy models like Lewis structures, VSEPR, hybridisation, etc... completely break down and you have to dig deep into the real science

MartianCactus

07:29

oh

nice

gannex

07:58

eventually you will become the orbital overlord

MartianCactus

lol

user228700

11:24

Hi :-) Can anybody please help me w/ this:

user228700

user228700

^ Which of these two structures is more stable?

user228700

I vote (b), because it looks like both structures have the same number of $\alpha$ hydrogen atoms and trans is more stable than cis, correct..?

user228700

The answer key tells me that the correct answer is, in fact (a)! How come..?

user228700

11:44

Can anybody tell me what a Canonical answer is?

user228700

I've started a bounty on my question:

user228700

1

Q: Is the inductive effect always measured relative to hydrogen?

Wikipedia has defined the Inductive effect thus: "In Chemistry and Physics, the inductive effect is an experimentally observable effect of the transmission of charge through a chain of atoms in a molecule, resulting in a permanent dipole in a bond." Recently, I learned from a teacher that t...

organic-chemistry electronegativity

user334283

12:00

I don't believe that it requires hydrogen to compare. Any atom or molecule which exhibits either +I or -I doesn't depend whether or not there is hydrogen atom around.

Bounty Hunter

1

Q: Is the inductive effect always measured relative to hydrogen?

Wikipedia has defined the Inductive effect thus: "In Chemistry and Physics, the inductive effect is an experimentally observable effect of the transmission of charge through a chain of atoms in a molecule, resulting in a permanent dipole in a bond." Recently, I learned from a teacher that t...

organic-chemistry electronegativity

orthocresol

12:21

@Kaumudi A canonical answer basically refers to a high-quality comprehensive answer that will serve as a useful reference for future readers.

I don't know about that alkene...

it's not cis, but rather 1,1-disubstituted (cis and trans refer to 1,2-disubstituted alkenes)

user334283

in simple answer No. Inductive effect is not measured relative to hydrogen. You don't require hydrogen to check whether an atom or a molecule exhibits +I or -I

Loong

10

Q: Stability of di-substituted alkenes

Well I know for a fact that cis alkenes are less stable than trans alkenes due to steric repulsions. But what bugs me is the fact that why systems such as 2-Methylprop-1-ene (where I believe steric repulsions are greater than that in cis-But-2-ene) are stabler than its cis and trans counterparts...

organic-chemistry stability

Martin - マーチン

12:39

@hBy2Py Brian, you are an active user of ORCA if I recall correctly. Did you ever install it yourself and do you have any recommendation for a nice little tutorial?

user228700

12:51

@Loong Thank you :-)

Jan

13:22

!!doi/10.1002/anie.201608795

Chemobot

Could not find the requested DOI : 10.1002/anie.201608795

Jan

@hexa you might be interested ;)

Hexacoordinate-C

@Jan what the .... O.o

This is an other hexacoordinate carbon ?

That is really fun

orthocresol

13:44

@Hexacoordinate-C pubs.rsc.org/en/content/articlepdf/1995/cs/cs9952400391

section 7 has a few 6-coordinate C

iupac.org/publications/pac/pdf/1993/pdf/6504x0691.pdf

hBy2Py

14:28

@Martin-マーチン Yep, I've got ORCA computations running at home on a dual quad-core Xeon server right now, as a matter of fact.

Installation is basically just extracting the archive to a folder and adding the folder to the path

The best starting point for recipes is the ORCA Input Library.

I've written a bunch of shell scripts to streamline my workflows; probably you should write your own, to suit whatever environment you set up.

ORCA works on queued clusters, but it can be tricky to get the environment set up properly -- I have no experience there, so if you're running in that enviro and need help, the forum is the best place to ask for help.

If you want parallel execution, you need to have OpenMPI installed. For v3.0.3, if you have a choice you should absolutely use v1.6.5. Other versions can work ok, but sometimes there are weird misbehaviors.

Loong

15:56

> But in theory, one and one carbon decides to leave behind it's friends bound by the diamond structure boundaries behind to seek their fortune in the hippie camp that is called liquid.

Bounty Hunter

16:28

1

Q: Modifying the conjugated system in litmus paper, by changing pH

I have been trying to understand the colour change in litmus paper from a quantiative point of view. I have knowledge of the particle in a box model of quantum mechanics, and i would like to apply this to the conjugated system in the active indicator-component of litmus dye. In other indicators I...

acid-base quantum-chemistry ph

Melanie Shebel

17:05

Wow, really growing that rep!

Off to take a phys exam. :S See you later!

Loong

@MelanieShebel good luck!

CowperKettle

17:40

> ,(?=[0-9])

I wonder what this Regexp line will find

ah, found a question

7

Q: Question mark with equal to sign in regex

Hey Experts i am new to regex.I am really confused by studying this regex.I have found something which is very difficult to understand for me.The thing is the use of question mark and equal to symbol in regex.An eg : "(?<=\d)(\s)(?=[\d-])" I just need to know the use of ?= in this regex code....

regex

hBy2Py

18:05

@CowperKettle Off the top of my head, I think that's a lookahead. A match will only be found for a comma with a following digit, but the returned match won't include the digit, just the comma.

Beware, implementation of lookarounds in the various regex engines out there is highly variable -- I've had a lot of trouble getting it to work in some cases. mainly bash shell scripts.

Hexacoordinate-C

@orthocresol I found that to help during the reading of the book youtube.com/…

theoreticalminimum.com

CowperKettle

18:33

@hBy2Py Thank you! Yes, it is that. I'm reading about that now

> ^(?<=[\d]{2})\.04\.(?=[\d]{2})$

Now I'm trying to concoct a regex that will help me replace dates looking like 12.04.16 with 13-Apr-2016

Zhe

18:59

Yours seems unnecessarily complex...

CowperKettle

That may be so! I'm a total rookie in regex

orthocresol

@Hexacoordinate-C some people like watching YouTube videos, some like reading books. For me, books work much better :p If you find something that works for you, that's good!

I've heard good stuff about Susskind's lectures, but just never really liked watching online lectures, so never bothered.

Hexacoordinate-C

I do both read and look

Hippalectryon

20:18

@paracresol Dat name >.>

@Chemobot o/

paracresol

@Hippalectryon What name?

Hippalectryon

@paracresol yours

paracresol

Oh and salut o/

Oh hi @Chemobot o/

:3

Lemme see how quick your creator is 3;)

!!img/@Hippalectryon

Chemobot

No result found.

Hippalectryon

@paracresol playing LoL right now >.>

paracresol

20:31

@Hippa I used to be @Aaron Abraham ._.

LoL?

Jan

@Hexacoordinate-C Yeah it is. I especially like it because it is a pure CH compound.

Hippalectryon

20:48

@paracresol League of Legends

paracresol

@Hippalectryon I don't play that ._.

I do Red Crucible Firestorm though ^_^

Hippalectryon

@paracresol It's fairly cool, try it when you can :-)

paracresol

@Hippalectryon What genre is it?

Hippalectryon

@paracresol It's a MOBA

What is League of Legends?

►

Melanie Shebel

I commented on this first answer to this question that perhaps in the future ask questions where the asker has put forth effort in their work.

0

Q: Arrange these compounds from the shortest bond length to the longest:

Given $\ce{SO2}$, $\ce{SO4^{2-}}$, $\ce{SO3^{2-}}$ arrange them from the shortest bond length to the longest. I actually did arrange them, but i am not sure (my answer: $\ce{SO3^{2-}}$, $\ce{SO2}$, $\ce{SO4^{2-}}$)

homework molecules molecular-structure covalent-compounds

paracresol

20:55

@Hippalectryon Wait...is this a Runescape rip-off?

Melanie Shebel

However another user said the work was sufficient

Hippalectryon

@paracresol No, not at all xD For starters it's not an RPG, every game you start over

Games last 30-60 mins

paracresol

Kinda looks like it...or maybe all RPGs haven't evolved past the Melee-Ranger-Mage characters XD

@Hippalectryon I see..

Melanie Shebel

I feel like a student could have written a huge homework question and arbitrarily wrote, "I got 4", is this correct as their "work."

Was my comment off base?

paracresol

But it still isn't my type though :(

Hippalectryon

20:57

@MelanieShebel I'm far from being a reference on CSE but I do side with you on this one, an explanation in the answer would be most welcomed

Jan

What made you arrive at that order? What is your reasoning? Did you just guess? — Jan 18 secs ago

Not sure what you wrote (it’s been deleted) but I don’t think that’s a keep-worthy question in its present state.

orthocresol

21:11

@MelanieShebel I agree with you and this is one of the reasons why I want to get rid of the effort requirement.

takes off mod hat Personally, I don't think simply saying "I got this answer" counts for effort. As a user, I would have VTCed.

puts on mod hat As mods, we only unilaterally close the very clearly zero-effort posts, so I didn't touch this one.

@Jan It read something along the lines of "please answer questions only when users have shown their thought process".

Can anybody please explain why this might be NAA?

0

A: Is mixing ammonia and bleach spray in the same parcel of air considerably dangerous to health?

In a poorly ventilated room, I'd certainly avoid using both at the same time. Ammonia is very volatile and will usually "find" the only slightly less volatile chlorine gas - or perhaps the bleach itself. -Chemist. PS: A poorly vented bathroom is in itself a bad idea. ;)

I'd like to see an experiment where the answerer's name and reputation weren't shown on the review page.

I feel that this is maybe a bad answer, but not NAA.

Jan

Hm, maybe. It seemed a lot like an off-track-ish comment in the review queue but I can’t retrace my train of thought at the moment …

paracresol

@Jan 'Course you can't...because the Truth is terrifying ;P

orthocresol

It might be better suited to a comment I suppose. We have the power to convert answers to comments :P

paracresol

@orthocresol Now what kind of sorcery is that -_-

orthocresol

It's fairly useful, because often new users post comments as answers because they lack the reputation to comment.

paracresol

21:29

FORGIVE MY IGNORANCE O @ORTHO!

Michael Harding

Can somebody please help me with part g of this question?

I think the Mr of whatever removed is 28 which could be a carbon and an oxygen.

But it has two less peaks in it's C13 NMR, which was originally 20

Jan

Well, you obviously need to remove two carbons with an Mr of 24. Leaving 4 that you have to remove. What could 4 equate to?

Michael Harding

Yeah hmm.

4 hydrogens xD but that would make no sense

Jan

So we have C2H4 that should be removed. That actually makes a lot of sense ;)

Remember that an alkane with n+1 carbons has a formula that corresponds to the n-carbon alkane + CH2 ;)

orthocresol

removing C2H4 reminds me of olefin metathesis..

Zhe

21:37

Also, the body is really good at hydrolyzing esters

Michael Harding

Hmm ah yeah

Jan

The thing is that you may want to remove C2H5 (the ethyl group) but then you need to remember to add back a hydrogen so that the acid becomes neutral.

paracresol

@Zhe ''Body"? Oh, @Jan and I were just talking about 'bodies' a while back; weren't we Jan? 3;)

Jan

Yeah, we were. Or still are. You’re denying the holocaust by the sounds of it.

paracresol

@Hexacoordinate-C o/

orthocresol

21:39

In the body the acid isn't neutral... This question is flawed. Downvotes and closes as unclear what you're asking

paracresol

@Jan Can we take that elsewhere ._.

Michael Harding

Hmmm....

We've been given a physics research task

And I'm considering using LaTeX

Just because

You know, it looks cool

Zhe

Wow, I've had a really unproductive day on Chem.SE, but I guess production fires need more attention... :/

Jan

@orthocresol But if you want to analyse it by NMR, you probably want to dissolve it in CDCl3, so you’ll need the neutral form. The question doesn’t say it’s in that form in vivo ;)

Loong

@Jan This sounds a bit like the old mathematics joke "… If now exactly one person enters the house then it will be empty again."

Jan

21:42

Reminds me of all the variants of ‘Two people go into a bus, three people come out. What scientists say what.’

Mathematician: If one enters now, the bus will be empty.
Biologist: There has to be a nest.
Physicist: We have a significant error in our data collection.

Hexacoordinate-C

So there is -1 person in the bus x)

Loong

@Jan Biologist: "They have reproduced."

Jan

@Loong Then the nest was the zoologist?

Hexacoordinate-C

@paracresol :)

paracresol

@Jan Zwei o ;)

Jan

21:45

@paracresol zologist?

Loong

@Jan I guess, there are much more variants.

paracresol

-_-

I meant just the 'zoo' bit ._.

Jan

@paracresol Inb4 @Loong mentions Pfeiffer ;)

paracresol

Anyways, I'm off! @Jan @Hexacoordinate-C o/

Hexacoordinate-C

@paracresol you are Hoff ?

paracresol

21:48

We'll deal with this ~~holohoax~~ holocaust 'issue' later @Jan :3

@Hexacoordinate-C Ja! I am Hoff!! KNEEL!!

I meant I'm going to bed ;P

Jan

Please continue reading Citrus while trying to fall asleep @para o/

paracresol

Huh? What're you talking about?

* Was Totally innocent*

Hexacoordinate-C

What's that?

paracresol

Until I met a certain someone ;0

@Hexacoordinate-C Nah, that's @Jan fooling around...Germans do that every now and then ._.

Hexacoordinate-C

A physicist, a biologist, and a mathematician are sitting on a bench across from a house. They watch as two people go into the house, and then a little later, three people walk out.

The physicist says, "The initial measurement was incorrect."

The biologist says, "They must have reproduced."

And the mathematician says, "If exactly one person enters that house, it will be empty."

paracresol

21:53

Not my thing ;)

Jan

@Jan @Para loves it, doesn’t he? ;p

paracresol

Apparently his senpai likes it better ;)

whoever that may be

:3

Hexacoordinate-C

@Jan the pic is too rude for my eyes

paracresol

@Jan DON'T DESTROY HIS EYES!

Zhe

We've wandered into NSFW territory...

Jan

21:55

Seriously, it’s on display in a bookshop. Not hidden or anything, right on public display ô.o But suit yourselves …

Hexacoordinate-C

@Jan I was joking but there are some youngs there ^^

hBy2Py

@Mart, @penta, others -- any thoughts?

1

Q: Matching a Slater-type wavefunction with a minimal (STO-nG) Gaussian basis set

I have on hand a high-precision wavefunction expressed in Slater orbitals. I need to express it as accurately as possible in a minimal Gaussian basis set. For background: I am currently working with STO-6G, but it is not good enough to describe the cusp condition with the accuracy I need. How c...

basis-set wavefunction

Jan

@Hexacoordinate-C *shrugs* Well, apparantly the second flag came through. I mean, they’re practically fully clothed and everything but w/e ^^

paracresol

@Hexacoordinate-C Yeah like me for instance (glares at @Jan)

Loong

@Jan If the flag came through, you would have been automatically suspended for 30 minutes.

paracresol

21:59

@Loong NOOOOO!!!

Jan

Oh, but the message is deleted?

Loong

@Jan Mod abuse!

Jan

Oh! =D

paracresol

@Jan OHHHH!!!

Hexacoordinate-C

@Jan is a really bad girl she'll need to be punish :P

Jan

22:00

Just avoiding further issues, I assume?

Oh she is. Like literally on the first page the bad girl’s punished the first time.

paracresol

@Jan Exactly!

Jan

For wearing make-up, iirc xD

paracresol

@Jan .....

Dammit I can't sleep because of ~~Yuzu~~ @Jan -_-

I hope you're happy -_-

Jan

Yes I am ^__^

Hexacoordinate-C

In a country in which people only want boys…every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

iflscience.com/editors-blog/…

Jan

22:05

@Hexacoordinate-C Going to guess 50:50.

Hexacoordinate-C

This a google interview question, I would not answer too fast ^^

paracresol

Wait.............

Dammit, I can't use Bayes' theorem here -_-

69

Q: Google question: In a country in which people only want boys

Hi all! Google published recently questions that are asked to candidates on interviews. One of them caused very very hot debates in our company and we're unsure where the truth is. The question is: In a country in which people only want boys every family continues to have children until ...

pr.probability co.combinatorics

Jan

Seems like Maths Overflow agrees with my gut feeling ^^

Zhe

@paracresol I'm pretty sure this is not a question we ask

Second of all, it's just a Markov chain...

@Hexacoordinate-C No, you should immediately jump on 50/50

Hexacoordinate-C

Lol

I would prefer to think before to act

Jan

22:14

But acting before we think worked so well all throughout history …

Zhe

I mean this may have been a old Google interview question

But it is almost certainly not asked anymore

There's no coding involved

orthocresol

Yeah I agree it's 50/50

Actually, maybe not:

Hexacoordinate-C

I remember during my chemistry oral competitive exam the last question was "what is the mass of the Eiffel Tower" with no data

Jan

> A lot.

orthocresol

Every family has 1 boy. The expectation value for the number of girls is $$\frac{1}{2}\cdot 0 + \frac{1}{2^2}\cdot 1 + \frac{1}{2^3}\cdot 2 + \cdots$$

Hexacoordinate-C

22:19

I found an answer very closed as said me the teacher

orthocresol

... which is equal to 1. wolframalpha.com/input/…

So, it is 50/50.

Jan

With every pregnancy, there is a 50 % chance that it’s a boy. Thus, this ratio will not change for very large number of pregnancies, i.e. an entire country. Whether or not couple A stops after two children while couple B stops after twenty-seven is irrelevant.

Zhe

Or, you can realize that each event is independent

And each event is 50/50

It doesn't matter why the event occurs

Only that the output from the event is 50/50

Hexacoordinate-C

I guess Google not ask the question to have only the answer

orthocresol

@Zhe hmm, fair enough...

hmm, I realise how to prove that that sum is equal to 1

Jan

22:24

Welcome to your job at Google, @orthocresol. You may not have known be we have been watching you since 2000.

orthocresol

Thanks, now can you please give me more Dropbox space?

Jan

Why am I reminded of the bastard operator from hell (bofh) now?

Zhe

@orthocresol, you're fired. you should have asked for more Drive space... :/

orthocresol

:D

Zhe

@Hexacoordinate-C Yes, process is important

So is coding. You wouldn't believe the number of people who can't write basic code.

Hexacoordinate-C

22:29

I don't think they want a code answer too ^^

My level in code is not so good, I solved the first 30 pb of the EulerProject after it becomes to be tricky but I'll try when i'll have time

Jan

bofh.bjash.com/bofh/bofh1.html

Hexacoordinate-C

I found 7462 Tons for the E.T.

Jan

Took me a second to realise you’re not talking about phoning home.

(Or The Game That Killed the Video Gaming Industry)

Hexacoordinate-C

x)

I remember they told me the a parameter of an allotropic form of iron and I needed to find the density of iron then the mass of the eiffel tower.

Zhe

@Hexacoordinate-C That's what I'm trying to tell you. I've done 13 interviews, and they all involve some level of coding.

Hexacoordinate-C

22:36

:)

@orthocresol I rmemeber you answer a question about absolute zero

PBS Nova S35E08 Absolute Zero; The Conquest of Cold Full Documentary

►

Zhe

@Jan I just realized that I typed a bunch of stuff, but if you look at what you wrote immediately above it, it's the same...

Jan

True story, mate ;)

Hexacoordinate-C

Theorem: 60 is even.

Proof: 5!/2 is the order of the group A5. It is known that A5 is a non-abelian simple group. Therefore A5 is not solvable. But the Feit-Thompson Theorem asserts that every finite group with odd cardinal is solvable, so 5!/2 must be an even number.

From MathOverflow

Hippalectryon

How can I change my login email ?

Hexacoordinate-C

Ask the boy who can make a chembot :)

Go in edit profil

priviate information

Hippalectryon

22:51

That unfortunately doesn't change the login email :(

Hexacoordinate-C

Oh

83

Q: How do I change the email address associated with my Stack Exchange OpenID?

I registered my Stack Overflow account using the Stack Exchange OpenID provider. I later changed my e-mail, but I cannot change the e-mail address associated with my OpenID for some reason. Why is that, and how do I change it? I logged in to Stack Exchange and it lets me change my password, but n...