Talk:Chemical reaction

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Note: a enumeration of the types of chemical reactions is needed

Edited by D.C.

We're going to have problems with some editors, because it seems they have no practical experience with what real chemists, in real usage, call a chemical synthesis. This corruption of use, which started in the chemical synthesis article, seems to be migrating to this article as well, and it will be stopped :). The next point is that this article should not be ended with a brainless enumeration of kinds of chemical reactions, but it could be well served by a series of links to Wikipedia articles on types of chemical reactions, articles which already exist within the Wikipedia. For example there already are articles on hydrolysis and one on the hydration reaction. Other articles on chemical reactions are embedded in the article on the compound itself (e.g. soap and saponification). Dwmyers 23:05, 10 Nov 2003 (UTC)

Contents

[edit] From PNA/Chemistry

  • Chemical reaction - This page needs a lot of work by someone with more chemistry knowledge than I have. The energetics of reactions need to be cleared up, and links made to pages like reaction coordinates, transition states, reactive intermediate, and such. There is a list of the "6 types of reactions", which other people have added to, with reactions that don't seem to fit into those six categories. The reaction rate section is almost nonexistent, the "Law of mass action" section is just one line (how about some history, or a more detailed explanation?). Finally, the "See also" list needs serious expansion.
This page could become a central point for articles dealing with chemical reactions, but as it stands, it is orphaned from a lot of them, and quite incomplete. --Kieran 12:04, 11 Apr 2005 (UTC)

[edit] More

This article was not written by a person with much knowledge about chemical reactions. Chemist is needed to rewright it. stone 6 Apr 2005

  • It's a tough job, even for a chemist! Physchim62 21:25, 15 Jun 2005 (UTC)
    • Especially since what at least I think is needed is a rather extensive restructuring of wikipedia articles (plural!). It is probably difficult to reach a consensus on such a structure (different fields of chemistry have a somehwat different way to look at these things). I'm a newbie in the wiki-world so such a task is way over my head, but maybe there could be a discussion somewhere on how to best structure information about chemical reactions, rate law, mass balance, chemical equilibrium etc. Other connected articles are Reversible reaction, Chemical kinetics, Exothermic reaction, Endothermic reaction, Gibbs free energy, Thermodynamics just to mention a few. The current structure seems to me as a bit waste of many peoples hard effort. By the way, there is a wiki book project on chemical engineering. Much of what's in the wikipedia (mentioned above) would be needed there too. Saittam 12 Aug 2005

[edit] Six types of chemical reaction?

Is this correct? Where do the additional reactions that have been added under this section fit in? I would like to fix that section, so the entries at the bottom of the list look like the rest of them, but I'm holding back because of the "six types" statement. --Kieran 11:10, 11 Apr 2005 (UTC)

  • That seems like a useful thing to fix but I think more pressing would be the fact that there are so many pages scattered around that this article links to. Some of these pages would be the types of chemical reactions. These could easily be put into this same article so that it is easier to access. Aznph8playa 00:44, 30 May 2005 (UTC)

There is always Category:Chemical reactions which this article could (and should) refer to... Yes, it's a big job, but... Physchim62 21:23, 15 Jun 2005 (UTC)

[edit] Level we're aiming at

The trouble with this stuff is that it's hard to aim it at the right level -as a degree chemist it's fairly hard to think back to when I didn't know anything about chemical reactions. Maybe I should borrow some chem textbooks for 13-year olds and see what they write?

Also why does 'compound' not occur in the introduction? argh! It really needs a full rewrite of the intro but not really sure what.

Excession 5 July 2005 08:23 (UTC)

I don't think we should be aiming at a 13-year old level: in France, the reaction formalism is introduced at about age 16 (class of Seconde), although we talk about chemical transformations before then. Thanks to all those who are trying to do something with this article, it seems beyond me to improve it for the moment however much it needs it! Physchim62 5 July 2005 08:41 (UTC)

[edit] E = mc^2 and chemical energy?

consider the reaction H + H -> H2 + Q

E = mc^2 is independent of the form of matter. and the energy contained on both sides of chemical reaction formula is equal. so is it right to assume the mass of H2 is slightly less than 2 H atoms?

Yes, indeed! Any transformation that involves a change in energy also involves a change in mass.--Nevermore78 01:20, 3 April 2006 (UTC)

Not so quick! Liberated energy in a bond-forming process like this comes from electron stabilization (that is, reduction of potential energy) due to, in a common way of describing it, the formation of more stable bonding molecular orbitals. There is no significant mass-energy coversion contribution on that. --Duplode 01:37, 3 April 2006 (UTC)

No, e=mc^2 applies to the actual energy of mass itself, not a chemical bond. Chemical reactions release chemical energy but only a nuclear reaction releases nuclear energy. In a nuclear reactor you actually get a little less fuel out then you put in.--Crucible Guardian 03:28, 6 July 2006 (UTC)

[edit] Chemical equilibrium

The phasing of the concept of an irreversible reaction seems oddly stif.

"This phrase means that nearly all of the reactants are used to form products. These reactions are very difficult to reverse even under extreme conditions."

'Used'? Would 'expended' fit better? And could we perhaps add an example of such a reaction? Combustion of methane or hydrogen seem to be less than ideal examples, but surely we can find an informative example. -- Ec5618 18:34, 1 February 2006 (UTC)

[edit] Example combustion reaction

C10H8 (g) + 12O2 (g) → 10CO2 (g) + 4H2O (l)

Does not combustion normally produce water vapour (gas, not a liquid)? Shouldn't the last element be 4H2O (g)? - Mike Rosoft 14:34, 10 April 2006 (UTC)

If you are using the equation to describe the process of measuring the heat of combustion at a temperature of 25C, then you give the reactants and products in their natural state at that temperature. Think of it starting at 25C, it burns and then everything cools back to 25C. The water condenses. The equation is correct. --Bduke 21:49, 10 April 2006 (UTC)
It's "correct", sort of, but describes a different process. This process doesn't involve only a chemical reaction, but also a heat transfer after the reaction has taken place. So, it's two processes bundled up for no good reason. --Vuo 01:13, 11 April 2006 (UTC)
It is not normal to put "+ heat" in a chemical equation. That is out of date useage. You might add the heat or rather enthalpy of reaction after the equation (ΔH = xx kJ/mol). It is clear that heat is given out because it is a combustion reaction. Your last edit is wrong. The states should be all at standard temperature or specifically 25C. What we want here is an exact correct balanced chemical equation. I'm going to leave it for now and see what others think. --Bduke 02:27, 11 April 2006 (UTC)
In fact, in that section, the phases are irrelevant. --Vuo 20:30, 15 April 2006 (UTC)

[edit] Thermodynamics section

As much of this article, the thermochemistry discussion here is unecessarly confusing and ambiguous. Why to discuss kinetics with two whole paragraphs on thermochemistry's lead? Or why presenting the general criteria of spontaniety (Gibbs Free Energy/Global Entropy) almost as an exception? Applying high school assumptions here won't make the topic that much amiable. I am thinking on a way of rephrasing things on that section, but I have not quite a solid formulation ATM. In the meantime, I invite fellow editos to clarify things - particularly if one knows some Physical Chemistry...--Duplode 05:26, 14 April 2006 (UTC)

Well....feel free to fix it! --Crucible Guardian 03:46, 6 July 2006 (UTC)

[edit] Phase Change

is a phase change 9i.e. evaporation or condensation) a chemical reaction? --Crucible Guardian 03:46, 6 July 2006 (UTC)

No, it's usually considered to be just a physical process in simple cases like water boiling or freezing. There are many cases where it could be considered as a chemical reaction - for example, solid sulfur is mainly S8, sulfur vapor is S2, so clearly some covalent bonds are broken in going from solid to vapor. Walkerma 07:01, 6 July 2006 (UTC)

[edit] By-product

Shoudn't there be a link to this page that allready links here ? samusz 12:22, 4 September 2006 (UTC)

[edit] reaction types

someone needs to reword the first sentence of this subheading, someone's idea of a sick joke.72.137.252.165 23:06, 5 September 2006 (UTC)

[edit] State Functions

I think we should edit the example equations to include state functions (g, aq, l, s) to help with understanding.71.111.98.144 03:26, 21 November 2006 (UTC)

[edit] Repeated vandalism

I tried to correct the current vandalism but couldn't see the original sentence (that was changed) at the beginning of the article. Also, looking back at previous revisions, there has been a fair amount of vandalism in the past. Aboyall 19:58, 24 January 2007 (UTC)

[edit] "Thermodynamically favored"

I reverted the recent change, back to "thermodynamically favored." This is a standard term in chemistry, and it gets over 83,000 hits in Google. By contrast, "favored in a thermodynamical way" gets no hits. Walkerma 05:27, 30 April 2007 (UTC)

[edit] Still not quite sharp...

It seems this particular article, by the pursue of simplicity in explanation and sharpness in classification, always has its focus, breadth and accuracy at stake. I have attempted to clarify some wordings and, more importantly, performed a number of deletions, which I put up for discussion:

On the classical definition, therefore, there are only two types of chemical reaction: redox reactions and acid-base reactions. The former involve the motion of lone electrons and the latter of an electron pair.

Overtly restrictive. Think of cis-trans isometization: one might argue the reaction can be mechanistically be described in terms of homo/heterolytic bond cleavage/forming, but it is doubtful whether saying the reaction as a whole is redox or acid-base is relevant or even viable. Or even better, think of pericyclic reactions.

Chemical reactions are also divided into organic reactions and inorganic reactions.

So people really think classification is important enough to go on the lead. Not to mention organometalic chemistry.

The collision of more than two particles into the ordered structure necessary to perform chemical transformations is extremely unlikely; which is why ternary reactions in practice are not observed. A chemical reaction may require three or more reagents, but the process can generally be decomposed into a stepwise series or a set of stepwise reactions of the above.

Although I have not removed this, it feels completely misplaced under the "Reaction Types" heading. And if "the above" refered to the list of types two paragraphs before, it was plain catastrophic constraining -hence, the rewording.

* Petrochemical reactions are often distinguished from other organic reactions.

So are biochemical reactions, or drug syntheses, or polymerizations, or...

Online Chemical Equation Balancer Balances equation of any chemical reaction (full or half-cell) in one click.

This looked like improper in regards to WP external link policy.

Finally a reminder: Going too far into adapting content to junior textbooks results in dellusion, even more so for those very juniors.

--Duplode 03:54, 30 September 2007 (UTC)

[edit] Standardized use of (s) (aq) etc. symbols is needed

Wikipedia must make up its mind which way to do things.

  • Ag2O(s)
  • Ag2O(s)
  • Ag2O(s)

67.171.43.170 (talk) 05:01, 10 December 2007 (UTC)