Sciencemadness Discussion Board - PbO or PbO2

PbO or PbO2

trinitrotoluene - 30-11-2002 at 17:06

If I did electrolysis on lead electrodes under some NaCl solution which form of lead oxide would I get?

vulture - 1-12-2002 at 09:07

None. You will get PbCl2 en maybe PbCl4. Both very toxic stuff so watch out.

madscientist - 2-12-2002 at 15:34

I'd think that you'd get mostly lead (II) hydroxide as a precipitate.

PbCl₂ + 2NaOH ----> Pb(OH)₂ + 2NaCl

PHILOU Zrealone - 24-3-2003 at 12:37

Most likely:
NaCl(aq) -e-> Na2(s) + Cl2(g)
Since
2Na(+) + 2e(-) --> Na2(s)
2Cl(-) --> Cl2 + 2e(-)
Na2 + 2H2O --> NaOH + H2(g)
NaOH -e-> Na2(s) + H2O2
H2O2 + Cl2 --> 2HOCl
2OH(-) --> H2O2 + 2e(-)
HOCl -e-> H2(g) + ClO-OCl
ClO-OCl + H2O --> HOCl + HO-ClO (etc formation of chlorites, chlorates and perchlorates)

Thus at one electrode there is Na2, H2 and on the other there is Cl2, H2O2, Cl2O2, HOCl,HOClO2,...
Pb in the presence of Cl2 will make first PbCl2 and then PbCl4!
Those will very fast precipitate Pb(OH)2 and Pb(OH)4!
Pb(OH)4 --> PbO2 + 2 H2O

When you think electrochemistry, you have to think half battery elements (electric equations) and also in terms of normal chemistry reaction involved at the electrode by reactive species with media species at that place!

Blind Angel - 24-3-2003 at 16:13

Alkali can come in the form of X2 ? i always though that only gas of halogen can do that

PHILOU Zrealone - 24-3-2003 at 16:30

See who is above the alkaline collumn on the periodic table of the elements?
H, Li, Na, K, Rb, Cs
H2 sounds familiar tor you?
Knowing members of a same family of elements display similar properties... Li2, Na2, K2, Rb2, Cs2

LiH, NaH so valence of Li and Na is one
HCl, HF so valence of Cl and F is also one
This explains why NaCl, LiF!

Also:
N2, S2 (other allotropic form exists), O2 (O3), F2, Cl2, Br2, I2

"Disodium"

forundretfrede - 26-3-2003 at 03:57

Its allways a little dangerous to extrapolate.......
To my best knowledge, sodium is a metal, and as far as I remember my band-theory, it will display metal-bonding. In popular terms, a soup of free electrons from the valence bands. This explains among other things the electrical condctivity of sodium.
Hydrogen is covalently bonded as dihydrogen, but sodium isn't!

PHILOU Zrealone - 26-3-2003 at 06:24

"Chemistry of the Elements:
N.N.Greenwood and A. Earnshaw

p85-4.2.4 Properties of the alkali metals:
The Group IA elemnts are soft, low melting, silvery-white metals wich crystallize with bcc lattices.Lithium is harder than sodium but softer than lead.
Lithium has a variable atomic weight wheras sodium and caesium, being mononuclidic, have very precisely known and invariant atomic weights.Potassium and rubidium are both radiocative but the half lives of their radioisotopes are so long that the atomic weight does not vary significantly from this cause.The large size and low ionisation energy of the alkali metals compared with all other elements have already been noted and this confers on the elements their characteristic properties.

The group usually shows smooth trends in properties, and the weak bonding of the single valence electron leads to low mp, bp and density, and low heats of sublimation, vaporization, and dissociation.Conversely, the elements have large atomic and ionic radii and extremely high thermal and electrical conductivity!!!"

True that I have found no real mention of diatomic sodium on the net (maybe in some Na vapour lamps).
But since all elements have free valencial electrons and that gathering those lower their energy vs the surrounding; all elements (but noble gases) form allotropic molecules!
So:
Monovalent atoms makes diatomic molecules
(H2,F2,Cl2,I2,Br2,Na2,K2,...)
Bivalent atoms form long chains or rings or doublets
(S2,S8,(S)n,O2,O3,(Ca)n)
Trivalent atoms from 3D structures,rings or sp doublets
(P2,P4,(P)n,N2)
Tetravalent atoms make 3D diamond like structure or graphitic sp2 2D planes!

I'm 99% sure diatomic sodium exists!

Blind Angel - 26-3-2003 at 09:41

i always thought that since Alkali metal tend to give electron to have their last electronic layer saturated, they couldn't form element between themselve.
If NaCl is Na-Cl+
So what is Na2? Na-Na+ the last one wouldn't be stable and i don't see how this can create covalencial link

PHILOU Zrealone - 26-3-2003 at 16:15

Following your logic:
HCl is H(+)Cl(-)

So what is H2? H-H+ the last one wouldn't be stable and i don't see how this can create covalencial link!
So what is Cl2? Cl-Cl+ the last one wouldn't be stable and i don't see how this can create covalencial link!

NAAAAAHHHHHHH! :mad:

Ionic link (100% polarised) (Cs(+)F(-))

Polarised covalent link (CCl4, CO2, F2O, H2S)

Pure covalent link (delta electronegativity equal to zero --> between 2 or more identical atoms --> for elements allotropes)
(O2,O3,N2,S8,P4,I2,F2,Na2,... and as one of the few exceptions PI3)!

:cool:

vulture - 27-3-2003 at 06:49

Most metals show the Na+ Na- ionisation in their crystal lattice. I have some pages of theory about it and I'll look it up when I have more time.

Na2?????

chemoleo - 26-7-2003 at 21:01

sorry, I would bet my money on it that it doesn't exist, under no conditions.
Hydrogen is H2, but only because its lowest orbtial is filled up. This is why helium is a noble gas, with its lowest shell containing 2 electrons. Now, Li, Na, K etc have one free electron and require 7 (SEVEN) more to be filled up. Thus, in terms of energy, the loss of one electron is favoured, so that the electron shell (the one below) is full. Na2 couldn't exist simply because an electron shell is neither filled nor reduced to the next lower orbital. Most elementary gases (except the noble ones) are diatomic because the electron orbital is filled up (i.e. they share it, and thus is less energetic and therefore more stable ... ) Chlorine, however can be 7+, i.e. in the case of HClO4. here, the more electronegative oxygen rips the electrons from the chlorine, so that the oxygen have filled orbitals, and the chlorine empty ones (approaching those of the next lower noble gas).
hope thats making sense

PS by the way, hydrogen actually CAN behave like a metal, i.e. with no molecular bond - this is under extreme pressures, then it's solid and a conductor. Apparently the core of Jupiter consists of metallic hydrogen. isnt that cool?

[Edited on 27-7-2003 by chemoleo]

too simple

tryptamine - 28-7-2003 at 18:30

chemoleo you would be amazed at what can exist under what conditions.

Your reasoning of "it won't fill or reduce to a 8 electron shell" is way too simple for chemistry more advanced than high school.

So....

Keep studying.

simple enough for you?

chemoleo - 28-7-2003 at 18:51

lol tryptamine...
I have studied already - thanks for ur constructive advice.
Of course this is a simplified view. of course there is more to this. does anyone really want a proper explanation (want a lecture on s & p orbitals?)? Just to say 'keep studying' certainly doesn't explain why there is no Na2, at least no Na2 as a gas or as a solid. I doubt very much that it ordinarily exists. Prove it before u make high quality statements like that. thanks

PS I *AM* amazed as to what can exist under certain conditions.

[Edited on 29-7-2003 by chemoleo]

blip - 28-7-2003 at 19:44

I read about metal bonding in my chem book. It talked about the electron "soup" and then how delocalized covalent bonding was more accurate in its description (eg. it explains the conductivity), although I wouldn't be surprised if there was ionization because... well, I don't know but I have a feeling it happens. Oh well.

thanks but no thanks

tryptamine - 28-7-2003 at 19:49

I've had plenty of lessons in s & p orbitals, In fact I give lessons in inorganic and organic chemistry to people like you.

And don't think I'm underestimating you. You don't know who I am do you? I'm not just a newbee here eh?

No one said anything about solids, but gasses are not excluded.

chemoleo - 28-7-2003 at 19:51

sure, there is electron delocalisation on a vast scale. this implies there are ionisations, but these are extremely short in time, and in constant rapid equilibrium, and very hard to observe (if not impossible) in real time

chemoleo - 28-7-2003 at 19:59

tryptamine...
very well then. I don't get lectures anymore, I am past that stage. So no lessons needed, especially from someone who generously advises to 'keep studying' without actually explaining a thing.
Show me some data on Na2 in solution or as a solid. This is what the whole discussion was about. bring it, newbee or not

you simplify once again

tryptamine - 28-7-2003 at 21:17

Well I didn't say anything about in solutions, I was just commenting on you saying it can't exsist.

I sure isn't anything you or I could make, or even hold in our hands if someone else makes it.

It can exsist just as can many bizarre compounds, but it takes experiments in phase chemistry and the kind of boring inorganic research I find unappealing.

You asking me to prove it has been made is just about as crazy as me asking you to prove it can be made. I don't exactly have immeadiate acess to all the inorganic papers published in the last 40 years at my fingertips. I can just tell you that it will exsist in some states for however breifly in time. You cannot tell me that there is some cosmic rule against two sodium ions sharing an electron.

And remember I never said you or I could make it or even keep it in a jar. There are hundreds of compounds that are seemingly impossible that are made and identified and decomposed in microseconds.

Let me ask what is your education?

... Na2??

chemoleo - 9-8-2003 at 17:39

ok, I think the discussion was about whether Na2 can exist in solution (see thread). and I think we all agreed that it does not. So I dont quite see why that justifies advising random people to "keep studying" in quite a derogatory manner.
Education got nothing to do with it, tryptamine, this is as far I know a forum where whoever with whatever grades/education can ask whatever she or he likes. Be it qualified or not. So I dont think you should judge forum comments by someones background you know of or not.
.... I guess we all agreed on that Na2 doesnt ordinarly exist, except in some mad conditions where Na2 decays within microseconds.... of which I am sure this is of very little interest to most people here... so wuts the deal? Surely there is a better way of contributing ur vast amount of knowledge in a more acceptable manner??

Peace

tryptamine - 10-8-2003 at 16:43

Peace.
This is as useless as a dick sizing competiton.

blip - 10-8-2003 at 17:07

How can Na2 not exist in solution? When putting a bit in water, doesn't some have to go in to start the reaction? Two attached sodium atoms could break off and exist in solution, not likely but possible. Boron often doesn't have an octet in its compounds:
<tt>
Boric acid

  ··     ··
H··O··B··O··H
  ··  ·  ··
      ·
     :O:
      ·
      ·
      H
</tt>
Although it's possible that the boron atom could coodinately covalently bond to an oxygen's lone pair (with resonance with the others), I was taught the above diagram was correct. Tryptamine's got a point.

pz

chemoleo - 11-8-2003 at 04:16

hehe.... tryptamine lets stick to the forum topic shall we? I like the ease at which you respond, going point by point thru a discussion

blip - I am not sure what u mean.... are u sure u want to continue discussing Na2 at the moment?

peace

Theoretic - 11-8-2003 at 07:58

Yeah, Na2 is theoretically possible, but with zero thermodynamical stability. Just nothing to hold it together.
A clump of 8 sodium atoms- yes, because there's an octet of electrons.
As for boron... well, yes, it does violate the octet rule sometimes, but by 2 electrons (so it's got 6), not by SIX like Na2.
Also phosphorus (as in pentahalides), but by two electrons as well.
Many strange compounds and molecules can be explained by electrons beng shared between atoms more than they usually are (which is what scientists do).
Edit: post 4 of the thread contains lots of reactions that are very improbable, yet are listed as main-sequence reactions.

[Edited on 11-8-2003 by Theoretic]

KABOOOM(pyrojustforfun) - 31-8-2003 at 20:23

here I try to bring up highschool level chemistry but in another way. generic formulas for covalent & ionic materials represent completely different data. eg: 1 mol(22.4 L) HCl is 1 mol Individual HCl units (HCl molecules)
but the formula NaCl just identifies relative proportions of ions. there's no individual NaCl unit in 1 mol NaCl there's 1 mol Na+ & 1 mol Cl- so due to the very strong electrostatic forces they arrange in a special lattice form depending on properties of the iones, in this example co-ordination number being 6. one may say 1 mol NaCl in a singlepiece crystaline is Na+602300000000000000000000Cl-602300000000000000000000

( some chemistry books present the reaction NaCl --> Na+ + Cl- for NaCl hydration, it is wrong or at least confusing. it's always Na+Cl- whether solid or dissolved.) most(all?) metals in crystal state are ionic! eg in 1 mol Na like 1 mol NaCl which was a lattice of equal mols of Na+ & Cl- there's a lattice of Na+ and e- so here we have free electrones instead of anions. and unlike anions in ionic salts, free electrons don't have a constant position in the lattice.

markx - 9-9-2003 at 04:20

A word on the original topic.....
When using lead electrodes in Na Cl solution one
would get the rather unsoluble PbCl2 on anode and it passivates the surface.
There's no way to oxidize Cl- ions on lead so no free chlorine, chorite or chlorate ions will form in this case.
Electrons are drawn from lead metal instead of Cl- ions and that leaves only one option- PbCl2
Pb(OH)will precipitate on cathode and it will corrode accordingly....

Theoretic - 29-9-2003 at 04:31

Correct me if I'm wrong...
Cathode:
Pb + 2H2O => Pb(OH)2 + 2H+
Anode:
2H+ + 2e- => H2.