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01:00 - 11:0011:00 - 22:00

1:08 AM
How many HBs can acetic acid molecule form?
(with anything)
Well, how many HBs does acetic acid form with water?
 
1:40 AM
Why must papers adopt the 2-column format? It is quite troublesome to keep scrolling up
2
 
 
2 hours later…
 
4:24 AM
wtf, I can't read it...might be a browser thing, hold on...
then I should get to bed
screw it, scihub here I come
 
What is F2^2-?
 
Difluorine dianion
 
@pentavalentcarbon I can't find anything about it
 
> there is no evidence for $\ce{F_2^{2–}}$ in the gas phase
> We are not surprised
as we recall the general observation that in the absence of
solvation or counterions, multiply charged molecular ions
are rarely stable relative to the loss of an electron and/or
bond cleavage
 
> The presence of F2^2– ion in the condensed
phase has been suggested as part of discussions of terms
of the NMR spectra of concentrated fluoride ion solu-
tions and explicit quantum chemical calculations of F2^2–
hydrates.
 
4:33 AM
But those chemical environments are very different.
Solvation of any weird species tends to be a very stabilizing interaction.
 
i'm more interested in its electron structure
all of its orbitals are filled
 
So here is something interesting about MO filling diagrams.
Sure, you can get information about relative energies and bond orders.
But because you don't know the absolute energies of the MOs, you can't tell if all the electrons are bound.
The comment about "multiply charged molecular ions are rarely stable relative to the loss of an electron"?
 
what does bound mean?
 
Certainly the second electron is in an MO above the ionization energy of $\ce{F_2^-}$,
Electrons are bound to atoms and molecules and ions, no?
Well, sometimes they like to become unbound.
The paper is saying that the 2nd electron won't stay attached to the ion without a lot of help.
It needs something to stabilize it.
This is why you tend to not see multiple anions.
 
By the way, since you cannot see it:
 
4:40 AM
(I did get a copy of that Science paper)
 
> Although 28 is overall a dication, the bonding about the central carbon is 10-C-5. Various types of evidence support our claim that it is in fact a TBP ten-electron species rather than the Td 8-C-4 species, 29.
So you can stop talking about how pentavalent carbon is a mistake
 
Please don't tell me pentavalent carbon isn't a mistake when you don't know what "electrons being bound" is...
Also both 28 and 29 are pentavalent.
 
@pentavalentcarbon true, can you teach me?
 
It's just a terminology thing.
You know how H2 has 2 electrons, right?
 
yes
 
4:44 AM
Those two electrons are said to be bound.
It's that simple.
 
eh, what
 
The electrons are bound to the molecule. They don't want to fly off unless you add sufficient energy.
Where are you in chemistry right now? Like, what part of your textbook or what topics?
 
no, i'm just researching about hypervalency to answer a question on main
@pentavalentcarbon you must know this: does your diamond form consist of atoms arranged in a hexagonal shape?
 
I've answered most of your questions, answer mine :(
that is, where are you in your chemistry education?
 
rate of reaction
 
4:51 AM
Ok, so that would be towards the end of a middle-difficulty high school class in the US.
 
yes
 
I think...that was a long time ago...
I don't know what my diamond form would look like since I would be hard US dollars that it doesn't exist.
 
0
A: Sudgen's concept of singlet linkage

DHMOSugden Above all, his name is Sugden, not Sudgen. What he said He did not say that the octet rule is never violated. On the contrary, he suggested that "the maximum number of electrons in the valency orbit can not [sic] exceed eight". (source) This means, while he denies that the octet rule ...

@pentavalentcarbon what, diamond does not exist?
 
5-coordinated carbon crystals? Nooooo
Diamond is tetrahedral, 4-coordinate.
 
well....
I just meant carbon
 
4:54 AM
Oh, well, of course it exists.
Yes, the vacancies look hexagonal, very much like cyclohexane.
I have never heard of Sugden, nor his singlet linkage. Hm.
 
that's why I needed to search
 
one tip though:
 
and I came up with pentavalent carbon
 
Rather than do this:
> Above all, his name is Sugden, not Sudgen.
in your answer,
make an edit to the question.
 
@pentavalentcarbon well, if this was the author's misunderstanding
then it would be better to leave it there
or else I would also not keep the second paragraph?
 
4:57 AM
I would personally make the edit because the incorrect name appears in the question title and it might mess up any searches.
 
please do make an edit
then I would delete the first paragraph
 
Ok, done, but it will have to go through review because I don't have 2000 rep.
 
@pentavalentcarbon Are you familiar the d-orbitals which you don't have?
 
bwaaaaaa?
No I am not
but I can give myself as many orbitals as I want in a calculation
 
Do you have any idea what z2 mean in dz2 orbital?
 
5:01 AM
yes
 
what does it mean?
 
It refers to the both the shape and the orientation of the orbital along the Cartesian axes.
(this site needs Flash, but is awesome)
See how it's aligned along the z-axis and has a different shape?
 
what does z2 itself mean?
 
That turns out to be very complicated and I won't go into it.
 
....
 
5:06 AM
I'm not joking, it really is.
You tend to not really understand what it means unless you take a very advanced undergraduate or graduate inorganic chemistry class.
Plus some quantum chemistry.
 
0
A: Sudgen's concept of singlet linkage

DHMOSugden Above all, his name is Sugden, not Sudgen. What he said He did not say that the octet rule is never violated. On the contrary, he suggested that "the maximum number of electrons in the valency orbit can not [sic] exceed eight". (source) This means, while he denies that the octet rule ...

another source yay
I have some knowledge of quantum
@pentavalentcarbon just explain please
 
You need to learn about group theory first and I am not going to teach you molecular group theory.
I am going to bed because it's 1 AM here.
 
@pentavalentcarbon I have some knowledge of group theory
 
...
I think I know what you're doing, I don't believe you
 
test me
 
5:11 AM
What's the point group of planar ammonia?
 
planar ammonia???
i dont know how you can make it planar
 
Flattened ammonia, all the atoms are in a plane...
It's a hypothetical molecule.
 
but ammonia is c3v
what
 
Well what is it in a planar shape?
 
it is still c3v because it has a lone pair
 
5:13 AM
I picked something you couldn't just look up on the internet.
...
That's not how this works.
I am forcing the atoms to all lie in the same plane.
What is the point group?
 
are you expecting c3h
i dont even know how u make it planar
 
It's hypothetical.
 
then it is d3?
 
No and no
 
alright
 
5:15 AM
D3 doesn't have any reflection planes.
 
im not very familiar
 
It's D3h. I need to go to bed.
(so you were very close)
 
alright
 
5:39 AM
-1
Q: Why Questions are marked as duplicate

Vidyanshu MishraWhen I was new on the stack exchange( now i consider myself an old member(1 month)),the problem i faced was most of my questions were marked as duplicate of other questions. I can't understand that why people mark some questions as duplicate,there are several possibilities,,maybe the person who h...

 
 
1 hour later…
7:00 AM
Why does HNO3 exist but not HPO3?
 
7:57 AM
@pentavalentcarbon it's a transition state for inversion :)
My only experience with comp chem so far was to investigate this energy barrier for inversion. And we found one imaginary vibrational frequency for planar ammonia. That was actually all we did haha
 
@orthocresol does the lone pair like go to the other side through the nucleus?
@orthocresol Would you be interested in this question?
1
Q: Structure of chromium trioxide

DHMOAccording to most sources, $\ce{CrO3}$ has the following Lewis structure (courtesy ChemSpider): However, it is also not planar (courtesy Wikipedia): Implying that there is a lone pair somewhere. What is the electron configuration of the $\ce{Cr}$ atom? Which orbital is responsible for the...

 
@MelanieShebel ok, I see.
 
8:23 AM
why does mercury cathode prefer reducing sodium ion rather than hydrogen ion?
@Loong
 
overpotential
 
eh....
why is there overpotential?
@AaronAbraham are you familiar with redox/chemical cells?
 
Sorta...why?
 
let's say I have a chemical cell consisting of two beakers connected by a KNO3(aq) salt bridge
 
(I'm still in high school...I doubt I'd be of much help though...)
 
8:36 AM
the left beaker has KI(aq) and the right has Fe2(SO4)3(aq)
 
Okayy...
 
the electrode is inert platinum
 
Fine...
 
connected to a voltmeter
which has reading
 
8:37 AM
so iodide ion is oxidized to iodine and ferric ion to ferrous ion
 
The reading please?
 
Don't care
 
problem: would my cell still work if I replace ferric sulfate solution by acidified potassium dichromate solution?
 
continue..
Give me a minute...
 
8:45 AM
@AaronAbraham any idea?
 
Yep...
 
which is?
 
Another minute, sorry.......I had to drink my coffee while it was still hot :P
Wait for it...
Wait for it....
Do you happen to know what the electrodes are made of?
 
13 mins ago, by DHMO
the electrode is inert platinum
 
Ah..
I don't seem to see a problem...the cell ought to work....
The reduction potential of potassium's ..
Is greater than that of iodine.....
 
8:52 AM
@AaronAbraham well, I thought anions are not attracted to cathodes
 
pretty much like your ferric...
Wait..
This is an electrochemical cell right?
 
chemical cell
not sure what the difference is
 
So the cathode here's positively charged....in an electrolytic cell the cathode's negatively charged...
This is an electrochemical cell...
 
what is this
 
10
Q: Are cations always positively charged?

Aaron AbrahamFrom what I was taught in middle school, cations are those ions that move towards the cathode, likewise anions are those ions which move towards the anode. I didn't have issues with this back then, since all we studied were electrolytic cells. But now that we've crossed over to electrochemical c...

An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt cell meant for consumer use. This type of device is known as a single Galvanic cell. A battery consists of two or more cells, connected in either parallel or series pattern. == Half-cells == An electrochemical cell consists of two half-cells. Each half-cell consists of an electrode and an electrolyte. The two half-cells may use the same...
An electrolytic cell is an electrochemical cell that undergoes a redox reaction when electrical energy is applied. It is most often used to decompose chemical compounds, in a process called electrolysis—the Greek word lysis means to break up. When electrical energy is added to the system, the chemical energy is increased. Similarly to a galvanic cell, electrolytic cells usually consist of two half cells. Important examples of electrolysis are the decomposition of water into hydrogen and oxygen, and bauxite into aluminium and other chemicals. Electroplating (e.g. of copper, silver, nickel or chromium...
 
8:56 AM
@AaronAbraham no. it is the positive electrode, but it is not charged.
and cathode attracts cations
 
......
The first link...shares my earlier confusion...
 
now, idea?
 
Let's clear up one thing first...
Cations are always positively charged right?
 
@AaronAbraham yes
 
The cathode in an electrolytic cell is negatively charged....but the cathode in an electrochemical cell is positively charged...
 
8:59 AM
@AaronAbraham well, i wouldn't call it charged, but whatever
 
....
Ah well, that's how I was taught it...
 
alright
@AaronAbraham where does this sentence come from?
 
Give me another minute will ya? I'm checking up the electrochemical series on Wikipedia....my textbook doesn't have 'ferric'....so wait a bit...
 
@AaronAbraham ferric just means Fe^3+
ferrous means Fe^2+
 
I corrected it a while back...
Now be a good water molecule and put up with me...
 
9:04 AM
@AaronAbraham what do you mean by good water molecule?
 
@Ramanujan look at my name
 
@Ramanujan DHMO = dihydrogen monoxide aka water
 
Ah i got it, dihydrogen mono oxide
 
(@DHMO, darn! You could've gotten him to sign that petition of yours ;) )
 
@AaronAbraham well, you mentioned water molecule first
 
9:07 AM
But he didn't get it back then..... whines ....
 
I'm trying to work here please...
 
Why last bond (CH) doesn't follow sequence of increasing of enthalpy of bond!
?
 
interesting
 
@DHMO can you answer?
 
9:11 AM
@Ramanujan i am thinking
 
Water molecules don't think....
(I'm typing out your electrochem. bit right now...)
 
@AaronAbraham thanks
 
@AaronAbraham after that please help me
 
@DHMO I'll ping ya after I'm done...
 
ok
 
9:18 AM
@Ramanujan C-H bond enathalpies. I guess the bonds in CH4 are sp3 hybrids, in CH3 they would be sp2 hybrids, in CH2 they'd be sp hybrids and in CH then the bond would be between a p orbital on the C and the H s orbital so no hybridization at all. Therefore a weaker bond and lower enthalpy
 
@GavinMachell nice explanation
 
@GavinMachell it might be
 
adding to @Gavin 's answer:
the C-H bond in CH4 is sp3-s
the C-H bond in CH3 is sp2-s
the C-H bond in CH2 is sp-s
the C-H bond in CH is p-s
@Ramanujan so the sequence is broken
 
@DHMO Keeping this in mind first: If a species has a high reduction potential it has a high tendency to get reduced, that is, it is a very good oxidizer. The reduction potential is inversely proportional to the oxidation potential. Going by the same logic...if a species has high oxidation potential it has a high tendency to get oxidized, that is, it is a good reducing agent. Reduction and oxidation potentials are inversely proportional to each other (Continuing...)
(The chat box doesn't permit long messages :( )
 
@DHMO Much more lucid than mine DHMO
 
9:21 AM
@GavinMachell it is based on yours
> If I have seen further it is by standing on the shoulders of giants.
2
-- Isaac Newton
 
"Satisfaction of one's curiosity is one of the greatest sources of happiness in life."
 
(Continued) If a species has a high reduction potential (high tendency to act as an oxidizer) then it is also said to have a low oxidation potential (low tendency to act as a reducer). Clear with this bit?
(Continuing...)
 
@AaronAbraham yes
 
(Continuing based on the electrochemical series from wikipedia)
  The values of standard electrode potentials are given in the table below in volts relative to the standard hydrogen electrode and are for the following conditions: A temperature of 298.15 K (25 °C); An effective concentration of 1 mol/L for each aqueous species or a species in a mercury amalgam; A partial pressure of 101.325 kPa (absolute) (1 atm, 1.01325 bar) for each gaseous reagent. This pressure is used because most literature data are still given for this value rather than for the current standard of 100 kPa. An activity of unity for each pure solid, pure liquid, or for water (solvent)....
Wait for it...
 
I'm trying very hard to deduce the bond order of CH3 from MO
 
9:30 AM
Side note: The reduction of 2H+ is arbitrarily assigned a neutral value- Zero volts, and I'll be referring to reactions (oxidation-reduction) as Upper-scale (having negative/low reduction potential) and Lower-scale (having positive/high reduction potential) reactions...
 
But I keep getting funny results
@AaronAbraham you're diverting now
 
(Continuing...)
Wait, @DHMO how?
 
alright, that's a side note, so I don't complain
please continue
 
O.o
(You do realize, my explanation is probably just going to be a substitute till Loong gets here...continuing anyhow...)
 
just continue
 
9:32 AM
Fine, fine...
In your first case, you dealt with 2I- +2e ----> I_2 in the left hand cell and Fe^3+ + 1e ----> Fe^2+ in the right hand cell (Continuing...)
 
you're just repeating my question, no offence
 
In your second case, you replace Fe^3+ with K^+ (None taken....and continuing......I'm trying to deal with the space limitations of the chatbox...so bear with me)
 
no i didn't
i replaced ferric ion with dichromate ion
potassium ion does not reduce
 
O.o
Why not?
 
look at the table
it is at the top
 
9:39 AM
The dichromate's supposed to be a spectator ion...just like the sulfate....(looking at the table)
 
nope.
dichromate is a strong oxidizing agent
 
in a redox situation, acidified dichromate is unlikely to simply "spectate"
@DHMO exactly
 
@GavinMachell forgive him, he's new to this
 
@DHMO Aah. I didn't realize you were playing devil's advocate.
 
9:42 AM
and you still haven't come to my problem
no offence, @AaronAbraham
 
( @Loong you're presence is urgently required at The Periodic Table )
 
@GavinMachell could you solve my problem?
 
What is it?
 
@AaronAbraham ?
 
> let's say I have a chemical cell consisting of two beakers connected by a KNO3(aq) salt bridge
the left beaker has KI(aq) and the right has Fe2(SO4)3(aq)
the electrode is inert platinum
connected to a voltmeter
which has reading
so iodide ion is oxidized to iodine and ferric ion to ferrous ion
problem: would my cell still work if I replace ferric sulfate solution by acidified potassium dichromate solution?
@GavinMachell @Loong ^
 
9:44 AM
(Now I'll play advocatus diaboli ....)
 
@AaronAbraham good luck
 
@Loong DHMO's problem's the problem...
 
@DHMO No, because the original cell had the Fe2+ being oxidised and you can't oxides dichromate
oxidise
 
@GavinMachell nope.
my fault, I meant ferric ion reduces to ferrous ion
 
(Playing my bit here: @DHMO 's argument hardly has any punctuation, he writes in clauses, doesn't format his symbols correctly, believes that the ferric is oxidised to ferrous, lays no emphasis on the voltmeter reading, nor does he mention how the voltmeter's connected. Gentlemen, clearly DHMO is asking a question not worthy of your consideration. It is a poorly framed question, peppered with errors of all sorts. I rest my case. Advocatus Diaboli out......
 
9:52 AM
Sorry, my booboo, Fe3+ --> Fe2+ in the original cell - that's a reductive process and that will drive the 2I- --> I2 in the LHS cell. So acidified dichromate will also work as a reductive process causing the oxidation of I-
 
O.o
@GavinMachell The K^+ is oxidized in the RHS cell, right?
 
@AaronAbraham nope
@GavinMachell my problem is... i don't think anion is attracted to cathode....
 
......
 
K^+ cannot be oxidized
it is already in the maximum oxidation state
 
@AaronAbraham Need a reductive process in the RHS cell
 
9:55 AM
CRAP.....hold it...I meant 'reduced'....thanks DHMO
 
K^+ does not reduce
 
it can, but it usually does not
 
No No
 
K^+ is very stable
 
9:56 AM
K^+ gets reduced...is what I'm saying..
 
no it does not... is what I'm saying..
 
emphasis on GETS...
Why not???
 
because K^+ is very stable
look at the table
it is at the top
 
Wait...then what happens to Na^+ when you electrolyze salt water?
 
depends on the cathode
it usually just stays in the solution
 
9:57 AM
You get hydrogen produced
 
unless the cathode is mercury
in which case mercury/sodium amalgam forms
 
In which case you get a sodium amalgam
 
Alright, my bad...
I capitulate....spare me the pain..
 
@GavinMachell my problem is, I thought anions do not get attracted by cathodes...
 
9:58 AM
Wait, I thought I already answered that part of the question...
 
See your point about the Cr2O4 2- ion. Gimme a mo with a pen and paper
 
@AaronAbraham no, you did not
 
the cathode is called the positive electrode
 
1 hour ago, by Aaron Abraham
The cathode in an electrolytic cell is negatively charged....but the cathode in an electrochemical cell is positively charged...
 
10:00 AM
it does not mean the electrode is positively charged
 
Now I'm totally lost...lemme get some water, arguing with DHMO's made me thirsty...
 
I am water
 
But you aren't exactly drinkable...no offense ..
 
@GavinMachell any idea?
 
Anyone happens to know if monomolecular-layers can be created on an adsorbent entriely through Chemisorption?
@pH13-YetanotherPhilipp Herr Thüringer, is physical chem your thing by any chance?
^^
 
10:10 AM
The dichromate system is electrochemically analogous to the Fe2+/Fe3+ system. It shouldn't matter that the dichromate ion is negatively charged to start off with. It should still suck electrons off the cathode and get reduced to Cr3+ creating an electrochemical potential. So, you'd get a reading of 0.79V. Now, if any current were to actually start flowing, i.e. if there would actually be a reaction - I doubt it.
 
@GavinMachell what do you mean by a reaction?
why doesn't it matter if the dichromate ion is negatively charged?
 
Well, with a perfect voltmeter - i.e. infinite resistance - no electrons will actually flow between the electrodes so no reaction will actually occur and the voltmeter will measure the full (theoretical) cell potential of 0.79V. If any electrons were to flow, then the cell would run into the problem you've identified which is that as electrons
build up on the electrode (I'm not going to commit as to whether it's the anode or the cathode) on the RHS then the dichromate ions are going to be repelled.
 
are you answering my second question?
 
@DHMO As far as calculating the cell potential is concerned, no, it doesn't matter. As far as the reaction actually proceeding, then yes, it does matter.
 
@GavinMachell but why doesn't the dichromate get repelled by cathode?
if cation is attracted to cathode?
 
10:19 AM
.....
 
@DHMO Well, it does, which is why I think the reaction would not actually proceed. But in terms of the cell potentials, which is basically the energetics involved, then the reaction is spontaneous and therefore you'd get a potential.
 
whaaaaat
 
@ DHMO Do you have a set of standard electrode potentials to hand?
 
yes
but for you to get any reading, you would have to have the reaction occurring?
 
@DHMO No, in fact, experimentally, you get values that are closer to the theoretical cell potentials when no reaction is occurring i.e. when the resistance of the voltmeter is infinite and no current is flowing. As soon as current starts flowing, then you get resistive effects occuring and the measure energy per coulomb drops.
 
10:27 AM
what... you mean the dichromate does not actually reduce to chromium ion?
 
@DHMO Well, not exactly, but it has the potential to. Hence the term "potential" difference!
 
@GavinMachell what.....
what on earth is this
 
@DHMO It's analogous to a working cell in an electric circuit. The potential developed by the cell drops as the resitsance of the circuit decreases.
 
I see
 
@DHMO So to get the most accurate reading between two actual half cells, you'd want zero current to flow in any case.
 
10:32 AM
I see
 
@DHMO Which means no reaction.
 
alright
but why is it depicted that reactions happen?
like in the usual cells
 
Because the chemical energetics work out okay. So, the chemical potential can be worked out as 0.79V. However, as you point out, if the reaction does proceed then the cathode becomes negatively charged with electrons coming from the iodide at the anode and that builds up an electrostatic barrier to the reaction of the dichromate, also negatively charged, at the cathode.
 
thank you
@GavinMachell why does permanganate reduce to +4 in alkaline medium but +2 in acidic medium?
(MnO2 and Mn^2+ respectively)
It amazes me, how most catabolic reactions are exothermic yet bond-breaking is endothermic; and how most anabolic reactions are endothermic yet bond-forming is exothermic.
 
@DHMO That's a very good question. The answer probably has a lot to do with the reduction potentials of H+/H2O/OH- Allow me to consult the table a moment.
 
10:40 AM
@GavinMachell ok, thanks
I'm sure OH- is not reduced
nor is it oxidized
@DHMO although pyrolysis and electrolysis are endothermic
 
@AaronAbraham just ask your question, but probably no ;)
 
!!img/performic acid
 
!!img/periodic acid
 
10:50 AM
@DHMO What happens during the electolysis of water? Hydrogen and oxygen are produced. Hydrogen at the cathode (where reduction of H+ occurs) and oxygen at the anode (where oxidation of OH- is happening)
 
yes
i have to go now
i'll come back soon
 
But to answer your first question, I think that it is mostly to do with the availability of H+. I've done plenty of oxidations using acidified manganate when I have ended up with a lot of brown MnO2 - usaully because I ran out of acid. It takes 8H+ to mop up all the oxygen on MNO7- to take the Mn all the way to Mn2+ If there isn't enough H+ (at high pH for example) then you get MnO2
That's almost certainly not the complete answer, but it fits.
MnO4− + 8 H+ + 5 e− ⇌ Mn2+ + 4 H2O +1.51
HO2• +  H+ +  e− ⇌  H2O2(aq) +1.51
That may well have something to do with it.
 
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