Sciencemadness Discussion Board

Nonstochiometric compounds, what, when, where, and why?

PokeChem - 12-10-2015 at 09:34

Why do they form? When to expect them? Are they unusual? What are they? Like PbO2, and many sulfides. For example in handbook of inorganic chemicals it says that Cu2S is maybe Cu1.8S, that FeS is maybe Fe0.86S, that NiS is maybe nonstochiometric.... Then what cation and anion is there. It must be something different. Help!!! I am starting to think that whole chemistry is a big lie, "so fools have something to lose time on, and to be happy in false hope". I mean, why in a hell, would something just like that, out of nothing, suddenly, be nonstochiometric?

[Edited on 12-10-2015 by PokeChem]

DraconicAcid - 12-10-2015 at 10:15

The copper one is easy- it's basically a mix of Cu(2+) and Cu(+). It happens because of entropy- a mix of two things is more stable than the pure substances.

PokeChem - 12-10-2015 at 10:36

Quote: Originally posted by DraconicAcid  
The copper one is easy- it's basically a mix of Cu(2+) and Cu(+). It happens because of entropy- a mix of two things is more stable than the pure substances.


What about PbO2? It says that the reason why the PbO2 is conductive is because there is some elemental lead. Can't oxides themselves be conductive? What about SnO2 (transparent conductor), is there the same as PbO2? Can those nonstochiometric become stochiometric by adding excess of one element, or by changing pressure or temperature? Is stochiometric PbO2, if it exists, conductive?

[Edited on 12-10-2015 by PokeChem]

Bot0nist - 12-10-2015 at 12:16

Hey, at least you've made a post not concerning "step one, build nuclear reactor. Step two, transmute "X" bullshit into gold. Step three, become ultra rich."
Refreshing in a way.
Unfourtunatly, you have answered your question in your own post...
Quote: Originally posted by PokeChem  
...I am starting to think that whole chemistry is a big lie, "so fools have something to lose time on, and to be happy in false hope".
[Edited on 12-10-2015 by PokeChem]


This is it, my friend. All of the posts on this board, as well as the several centuries of chemical and alchemical knowlage have been nothing but a vast and long running ruse, engineered for the soul purpose of confusing you and giving you false hope. It is all a hoax man, a gag, and you have been had. Now that you are finally on to the joke, it is pointless though, and chemistry work and research will now cease to be "done."

You hear that, guys? The gig is up. We can all FINALLY give it a rest...
:D

[Edited on 12-10-2015 by Bot0nist]

szuko03 - 12-10-2015 at 12:19

^^^ Quick everyone into the Physics department, I think we can keep the charade going there!

aga - 12-10-2015 at 12:46

Where is that ?

I'm in the Botany Department, Armstrong Foundation Wing, Level Delta, Corridor 7, Door 3F.

(formerly the SU Bar, and they have not taken the beer out yet, so i thought i'd help them).

[Edited on 12-10-2015 by aga]

PokeChem - 12-10-2015 at 13:36

Seriously, a big lie. How can I know that elements exist? I have never seen an atom, isotope, or neutron. Some sources give extremely big differences on data for melting point / density / boiling point... They say "maybe"..."probably"..."dubious"..."predicted"... And like some isotopes exist. Some numbers, balls, dots. And they gave half lives so I can know will I be irradiated. And that was not enough, but they gave some isomers and say "probably more exist". Like they wanna say: "it exists, but don't try to check it yourself, because you can never know what you have". And that was not enough, but I can't know even color or density of element/compound, because some compounds have allotropes. Then I can't even distill something, because it probably decomposes. Then all values for solubility are different. Crazy.

For example even such simple compound as FeCl3 is not fully described. Some say it decomposes above 300 Celsius, some say it can be distilled...

Then consider fractional distillation. One compound boils easier than another, but together they both boil easier than each. NurdRage talked also recently about it. So I can't even distill something.

Then I don't know what will get reduced rather? That say that regardless of reduction potential, the compound which would rather oxidize, might be reduced, because of lechatelier principle, or because reduction potential changes with temperature. Then I don't know is electronegativity or reduction potential more important. For example Cs would oxidize bedore Li according to electronegativity. But Li would first according to reduction potential.

Then I don't even know the name and structure of some compound. For example nitrogen trichloride. It doesn't exist. They say it's (very likely) chlorine[1] nitride.

Then we don't know is something phosphorus hydride or hydrogen phosphide.

Then there is no gold compound which has boiling point.

I just can't believe! For example nobody even discovered how to distill water. Because when you distill it, also P, S, Se, organic compounds will boil together and not get separated.

Then mercury or gallium can go through containers in which they are held, and probably through my skin.

Then some particles are going through our body all the time? Neutrinos, then natural isotopes which are slightly radioactive.

Looks like, just nobody knows nothing.

aga - 12-10-2015 at 13:56

You can't have any absolute proof : everthing we imagine we know could simply be an Illusion or a Lie.

Ignoring that fact and carrying on is what is called Faith.

Your argument against Science should really start with the Fundamentals, such as eyesight, smell, sense of touch, memory etc, each of which may be simply manipulated by Lizard Aliens, obviously.

If you accept that there is no Absolute Truth, what to do ?

Talk a lot, rant, fart into a tin basket ?

Well, you can if you like, i'll carry on exploring the 'known' accepting that it may well be inaccurate, or plain wrong in some areas.

Certainly i'd not choose to just Talk a lot to random people (although i have been known to do that on occasion) and count myself as 'doing something'.

Doing Things to find out while measuring everything as we go works pretty well in most eventualities, and i think that is what is called Science.

Science : Madness. There need be no absolute distinction.

CharlieA - 12-10-2015 at 16:07

Aren't all "non stoichiometric compounds" just mixtures?

j_sum1 - 12-10-2015 at 16:25

Quote: Originally posted by CharlieA  
Aren't all "non stoichiometric compounds" just mixtures?

No. Very common to have deviations from stiochiometric ratios in minerals.
Consider a form of limestone (Ca, Mg)CO3 where an indeterminent proportion of the Ca has been substituted by Mg.

Or intermetallic compounds. Suppose two metals A and B nominally form the intermetallic comppound A3B There may be some lattitude in that ratio which causes the crystal matrix to become strained but still stable. Hence A2.96-3.04B

CharlieA - 12-10-2015 at 16:54

Quote: Originally posted by j_sum1  
Quote: Originally posted by CharlieA  
Aren't all "non stoichiometric compounds" just mixtures?

No. Very common to have deviations from stiochiometric ratios in minerals.
Consider a form of limestone (Ca, Mg)CO3 where an indeterminent proportion of the Ca has been substituted by Mg.

Or intermetallic compounds. Suppose two metals A and B nominally form the intermetallic comppound A3B There may be some lattitude in that ratio which causes the crystal matrix to become strained but still stable. Hence A2.96-3.04B[/rquot


Interesting! Can you supply a reference to this subject? I guess I confuse minerals with rocks. Thanks