Talk:Chemical equation

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Do not use subtext to mark the state of matter of a material in the equation.
NaCl(aq)+AgNO3(aq)→AgCl(s)+NaNO3(aq) ${\displaystyle \surd \!}$
NaCl_(aq)+AgNO_3(aq)→AgCl_(s)+NaNO_3(aq)${\displaystyle X\!}$
--Derg(hu.wikipedia.org)--81.182.49.127 (talk) 10:40, 4 January 2009 (UTC)[reply]

I'm going to try and overhaul this article to be clearer, as well as expand what is presented. I've already started deleting the how-to information presented. I plan on providing some graphics to explain the parts of a chemical equation among other plans. Chemeditor (talk) 23:28, 6 October 2008 (UTC)[reply]

I propose merging Ionic equation into a subsection of the chemical equation article because ionic equations really are just a subset of the more general idea of chemical equations. Considering the limited information presented in both articles, it would be best to combine them. Chemeditor (talk) 22:54, 5 October 2008 (UTC)[reply]

I also suggest adding Molecular equation into the main article for the reasons above. Chemeditor (talk) 23:03, 5 October 2008 (UTC)[reply]

I've gone ahead and merged the two other articles into this one. Chemeditor (talk) 02:33, 10 October 2008 (UTC)[reply]

But I ask someone to add some better method for equation balancing since what is there although is kinda practical reasoning, it's not so suitable for complex cases and also takes a lot of text to explain(someone should clean that up too). But what I really want is to suggest a description of linear systems balancing, which I find much more effective and elegant. I will give an example:

K₄Fe(CN)₆ + H₂SO₄ + H₂O → K₂SO₄ + FeSO₄ + (NH₄)₂SO₄ + CO

The method consists in the following:

1. Assign variables to each coefficient:

a K₄Fe(CN)₆ + b H₂SO₄ + c H₂O → d K₂SO₄ + e FeSO₄ + f (NH₄)₂SO₄ + g CO

2. We must have the same quantities of each atom in each side of the equation. So, for each element, count its atoms and equal both sides:

K: 4a = 2d

Fe: 1a = 1e

C: 6a = g

N: 6a = 2f

H: 2b+2c = 8f

O: 4b+c = 4d+4e+4f+g

3.

d=2a

e=a

g=6a

f=3a

b=6a

c=6a

which means that we have all coefficients depending on a parameter a, just choose a=1(a number that will make all of them small whole numbers) and you'll have:

a=1 b=6 c=6 d=2 e=1 f=3 g=6

4. And the balanced equation at last:

K₄Fe(CN)₆ + 6 H₂SO₄ + 6 H₂O → 2 K₂SO₄ + FeSO₄ + 3 (NH₄)₂SO₄ + 6 CO

One could argue that this method requires much more work than the other, for that reason I will show that combining both can lead to a very efficient and quick way of balancing(although for very complex cases I would keep this one in the pocket):

1. Identify elements which occur in one compound in each member(this is very usual)

2. Start with the one among those which has a big index(this will help to keep working with integers), and assign a variable, let's say a.

a K₄Fe(CN)₆ + H₂SO₄ + H₂O → K₂SO₄ + FeSO₄ + (NH₄)₂SO₄ + CO

3. Well, K₂SO₄ has to be 2a(because of K), and also, FeSO₄ has to be 1a(because of Fe), CO has to be 6a(because of C) and (NH₄)₂SO₄ has to be 3a(because of N). Well, this takes out the first four equations of the system! We already now that, whatever the coefficients are, those proportions must hold:

a K₄Fe(CN)₆ + H₂SO₄ + H₂O → 2a K₂SO₄ + a FeSO₄ + 3a (NH₄)₂SO₄ + 6a CO

4. We can continue by writing the equations now(and having simpler problem to solve) or, in this particular case(although not so particular) we could continue by noticing that adding the Sulfurs we get 6a for H₂SO₄ and finally by adding the hydrogens(or the oxygens) we get the lasting 6a for H₂SO₄.

5. Again, having a convienient value for a(in this case 1 will do, but if a gets fractionary values in the other coefficients you will like to cancel the denominators) we get the result:

K₄Fe(CN)₆ + 6 H₂SO₄ + 6 H₂O → 2 K₂SO₄ + FeSO₄ + 3 (NH₄)₂SO₄ + 6 CO

Rend 03:06, 10 August 2005 (UTC)[reply]

I added it as I described it here, I think it need to be better written although. Rend 04:21, 19 December 2005 (UTC)[reply]

I don't know if this helps anyone but I thought I would mention that the reverse arrows display as boxes in MSN Explorer 9.2 64.114.88.154 23:14, 30 March 2006 (UTC)[reply]

I thinik this method for balancing chemical equation is very appropriaye and suitable .Teacher should Be encouraged to use this method to teach teach their student even this method should be added in the cource.I unterstood ths method for chemical equation. — Preceding unsigned comment added by Rahul Prasad wagle (talk • contribs) 02:27, 1 April 2016‎ (UTC)[reply]

I'm concerned about this article because it reads like a how-to guide and Wikipedia directives explicitly state that Wikipedia is not supposed to be a how-to guide. Perhaps we can clean this up? -SocratesJedi | Talk 03:48, 28 January 2007 (UTC)[reply]

I agree this article reads mostly as a how-to; particularly the Balancing Equations section. I recommend keeping Ex. 1 from the Balancing Chemical Equations section and moving the rest of the section into a WikiHow or WikiBooks article. That would get across the important point, namely matter cannot be created or destroyed during a chemical reaction. The rest of the examples serve only to describe how to balance an equation; they provide no new information about chemical equations. Chemeditor (talk) 19:02, 5 October 2008 (UTC)[reply]

They seem to share the same scope. Maybe we should merge them? P3net 00:14, 7 March 2007 (UTC)[reply]

I do not think this would be appropriate. A chemical formula does not imply an equation. For example, NaCl is an example of a formula, but is not an equation. On the other hand, Na + Cl --> NaCl is an equation that contains formulas. Chemeditor (talk) 19:07, 5 October 2008 (UTC)[reply]

maybe you can add the identifications of the different symbols used in solving chemical equations? that will be a big help... thanks —Preceding unsigned comment added by 124.107.87.250 (talk) 02:48, 25 November 2007 (UTC)[reply]

The article doesn't explain what the state symbols mean, it just jumps into using them. The symbols I'm talking about are: (aq),(I),(S), ... etc... Like: AgCl(s) I remember that (aq) means aqueous, but its been a while since I took chemistry and don't remember the others.75.82.133.73 (talk) 12:28, 18 October 2008 (UTC)[reply]

Are any of them viable per WP:EL? Looks to me like just a bunch of random "yet another" teaching/practice-problems or reaction-balancing applets. Might be a good pile for DMOZ, but not here IMO. DMacks (talk) 21:50, 2 February 2009 (UTC)[reply]

In the net ionic queation example, the precipitates is marked as solid (s), but the ions aren't marked as aqueous (aq). As my current chemistry proffesor keeps reminding me, a chemical equation must have all chemical states labeled "or it's wrong." I'm not sure if that is his opinion on the matter (no pun intended), or if he's trying to teach the scientific standard. Could an expert check this? NickNackGus (talk) 23:08, 8 October 2012 (UTC)[reply]

I cannot find that requirement in anything authoritative, such as IUPAC rules. But your textbook might include it as a best practice or in the context of learning about the nature of the chemical changes (up through intro-college level), and therefore your professor might require it when grading assignments on those topics. It is an explicit indication of more of the changes that is occurring (not just the ions combining and becoming a solid result, but also that they become desolvated). "The physical state of chemicals is also very commonly stated in parentheses after the chemical symbol, especially for ionic reactions" (emphasis mine). I added a comparative example to the article. DMacks (talk) 14:12, 10 October 2020 (UTC)[reply]

In the example equation for dehydration of methanol to dimethylether I am using a dash to explicitly show the single bonds between carbon and oxygen:

${\displaystyle {\ce {2 CH3-OH -> CH3-O-CH3 + H2O}}}$

It is an attempt to make the functional groups, which are directly involved in the reaction, easier to spot, given that this article introduces some of the most basic reaction equations. It seems however, that this formula style is not very common, so doubts about my decision have come to my mind. Should the dashes be removed to get ${\displaystyle {\ce {2 CH3OH -> CH3OCH3 + H2O}}}$ ? Petr Matas 23:10, 29 June 2022 (UTC)[reply]

Explicit dashes are not used in chemical equations unless the intent is to specifically highlight changes in bond order caused by the reaction. Qflib, aka KeeYou Flib (talk) 01:55, 30 June 2022 (UTC)[reply]

 Done. Petr Matas 03:10, 30 June 2022 (UTC)[reply]

If your goal is to emphasize the actual changes that occur and retain the idea of functional-group changes, rather than emphasizing the fact that "2 methanol in, methyl ether out", it might be written:

${\displaystyle {\ce {H3COH + HOCH3 -> H3COCH3 + H2O}}}$

You could also (or instead) use color to empasize the functional-groups involved, making the "OH" units and the O and H2O in the product red or something. Depends what your main point(s) are. DMacks (talk) 03:58, 30 June 2022 (UTC)[reply]

I want to emphasize "+ water out" and then manipulate this part of the equation. Petr Matas 07:36, 30 June 2022 (UTC)[reply]

The section entitled "Notation variants" introduces notation that I have never seen before, and does so without using any citations to reliable sources. t seems to me that the entire section should be removed unless some reliable citations are introduced. Qflib, aka KeeYou Flib (talk) 02:01, 30 June 2022 (UTC)[reply]

I believe that at least the first two variants are well established and someone will surely be able to find reliable sources. For example here at Wikipedia we have the article Hydrolysis with this figure. What I don't know is whether such figure can be said to consist of chemical equations. You may be right about the last variant (product on the left-hand side). However many high-school chemistry students tend to use it as an analogy to math equations, even though it may be considered incorrect (see the ref to Stack Exchange). That is why I believe it is worth noting (at least as a bad practice) and it should be possible to find something about it somewhere. ;-) Petr Matas 02:43, 30 June 2022 (UTC)[reply]

These are steps in a reaction mechanism. I don't generally think of these as chemical equations, which have a different purpose. But I agree that it can be included, but it must be made clear what context it's used in. So now that you've explained it, go ahead and write about it, but include references. Qflib, aka KeeYou Flib (talk) 02:52, 30 June 2022 (UTC)[reply]

@Qflib: which specific notation is new to you? The reactions going around in a circle? The use of lines to separate groups within a condensed structure, or something else? A multi-step reaction sequence (or a step-wise mechanistic process) can be written in any visual direction; the chemistry "follows the reaction arrows". It might be wrapped around in order to save space. Or to bring certain structures into visual proximity if one is writing prose that discusses their relationship. Or to allow reaction-arrows to connect different stages (rather than a strictly linear process). Literally any orgo textbook will have these. Biochem (File:Calvin cycle.svg) and organometallic (File:Suzuki Coupling Full Mechanism 2.png) are fond of cycles. Journal articles studying reaction mechanisms and pathways will have all sorts of crazy directions and multiple routes between given structures. The best illustration of a reaction depends on what specific details one is trying to emphasize. Pick a type you'd like to see, I'll find you an example. DMacks (talk) 04:07, 30 June 2022 (UTC)[reply]

@DMacks: How would you write about the difference between chemical equation and a multi-step reaction sequence (given that according to Qflib the notation variants may only be suitable for the latter)? I also see that in both example figures with instances of reactants above the arrows, those are without the plus sign, just like

${\displaystyle {\ce {CH3OCH3->[{\overset {}{\ce {H2O}}}]2CH3OH}}}$

This confuses me, because I thought that this notation is reserved for catalysts. I would expect

${\displaystyle {\ce {CH3OCH3->[{\overset {}{\ce {+H2O}}}]2CH3OH}}}$

Should we mention that both variants are possible? Petr Matas 08:07, 30 June 2022 (UTC)[reply]

Of course, the Krebs cycle notation is clear. TBH I couldn't see that image at all on my screen when I first read the page. I never had any objection to the image - never even saw it. I was simply confused by the presentation that was being used because no context was being presented for its use, and the rest of the page is focused on the use of balanced chemical equations for stoichometric purposes. It's perfectly fine to have this section and explain the use of this notation, it just needs to be made a little more clear. Qflib, aka KeeYou Flib (talk) 15:08, 30 June 2022 (UTC)[reply]

I hit "return" a little too quickly there. PetrMatas, mentioning that both variants are possible makes sense to me. Qflib, aka KeeYou Flib (talk) 15:10, 30 June 2022 (UTC)[reply]