user116211
1:54 AM
@MelanieShebel There is an invisible ok botton. See the lighter white box on the bottom left; click on it. It'll go away.

3:28 PM
Hello.
I though in chemistry equations - the chemical used are what they are and not like 1 mol of them.
I mean like for example:

2 H2 + O2 → 2 H2O
Means that 2 molecules of H - the first part.
And not 2 mol of H.
It's subscript - the 2 after H.

$\ce{2 H2}$ means 2 molecules (or moles) of $\ce{H2}$
you can think in terms of individual molecules
you can think in terms of moles
there is no difference

How is there no difference?
"The mole is the unit of measurement in the International System of Units (SI) for amount of substance. It is defined as the amount of a chemical substance that contains as many elementary entities, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of carbon-12 (12C), the isotope of carbon with relative atomic mass 12 by definition. "
Quoting Wikipedia.

And what?
Where do you see any contradiction with what I've said?

Well if the element is not carbon-12 (12C).
There should be a difference.
Isn't that so?

I repeat what I've said: one can interpret stoichiometric coefficients both as the numer of molecules as well as the number of moles.

3:41 PM
Like if the the element in the equation is not like :

2 carbon-12
But they are different things right?
However it doesn't matter how it's interpreted.
Am I getting this right?

Moles and molecules? Sure, their are different things.
Yes, it doesn't matter.

OK thanks - I understand now.

Because 1 mole of every substance contain exact same number of molecules.
The number of molecules in a mole is known as Avogadro's constant... bla-bla-bla
From the same Wiki page you cited.

Which maybe means it will be the same if I multiply the coefficients by some number?
In a chemical equation.

yes, you can think first that the stoichiometric coefficients shows the numer of molecules
but since you're free to multiply them all by some number (it's en equation)
you can multiply them all by Avogadro's constant
and interpret the stoichiometric coefficients then as the number of moles

3:50 PM
Well I was asking because there was some rule in thermochemistry that I'm learning now which was valid only if the produced substance is a single mol.
But I can't exactly translate it now.
Anyway I think I got this for now.

2 hours later…
5:29 PM
Y IZ DIS CAT NOT ACTIV WEN I IZ HERE?!

:O

O:

(0:

:0)

6:39 PM
Am I missing something but what's the point of specifying the state of matter in a chemical equation if we know that it's in the standard conditions?

@FISOCPP Nothing, really. :P
Depends on what you call "point".
It just gives info. That info is usually useful.

So it's just optional?

Yes.
They may require you to write them though, in thermochem calculations.

This is just where I encounter them.
Why though?

Since for example the enthalpy of formation for H2O(g) and H2O(l) is different.
States matter in calculations, that is.

6:44 PM
Or maybe in the case they doesn't matter because something?

First, not all reactions happen in "STANDARD CONDITIONS".

Well it looks like that is kinda implicitly implied - at least in my grade.

Second, some reactions are highly exothermic, resulting in the evaporation of chemical that would otherwise have been a liquid, or a highly endothermic, resulting in condensation or fusion.

OK - thanks for the info.
I'll keep that in mind.

For instance, it's H2O(g) not H2O(l) when you burn alkanes.
But water is a liquid in RTP.

6:51 PM
Well in that case the state matters in the product then.
When in standard conditions.

RTP = Room Temperature... ?
I wonder how can one possibly deduce this reaction logically
Should one just role-learn dozens of reactions?
It's interesting when exactly chemists knew for the first time how to determine the structure of an unknown organic molecule.
Or maybe it's still guesswork.

7:42 PM
@CowperKettle at least in this case, yes. the more common abbreviation is r.t.

2 hours later…
9:14 PM
@Manish o/
6

Follow up of Throw in an idea for TRE (II), and taking the advice in the answers into account, and coming up with an optimal time for TRE. Please write an answer to declare that you'd like to participate in the event. Please issue three time ranges: The Optimal Time Range: Hours of the days y...

@Wildcat @pH13 @Loong What do you think guys? ^

2 hours later…
11:06 PM
@CowperKettle RTP = room temperature and pressure. RTP is used more in thermodynamics, whereas r.t. is more commonly written when describing organic rxns.

chemistry.stackexchange.com/users/24052/mhchem - this mathjax guy made more than hundred edits o.o
There should be a bot for this, or he should get flood flag or sth

11:22 PM
@Mithoron I know...he is changing every instance of the MathJax \cf function for chemical formulae to \ce, presumably because a future version of MathJax will deprecate \cf . (Un)fortunately, I seemed to be the only regular user who ever used this function.
So now all my old answers are back on the main page...
I guess I"m getting lots more upvotes from this, which is nice, but yeah it would have been way better if there were a behind-the-scences automatic way to make this happen without pushing everything up to the main page again.

@CurtF. Haha, lucky guy ;) Still he tries to accumulate edits to reduce impact, as he should do.
Wow, Jonsca too rest of reviews. Heh it's like TRE came back earlier @IͶΔ :)

11:53 PM
indeed, I'm not sure I ever hit the daily cap for reviewing edits until today..