Talk:Stoichiometry

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Old discussion[edit]

Why does the Stoichiometric air-fuel ratios of common fuels section need to be in here? It seems random and out of place. 129.118.97.125 (talk) 21:19, 21 January 2009 (UTC)


This article has used different markup styles:

2H2 + O2 --> 2H2O
2H2 + O2 --> 2H2O

Both styles are typographically inadequate. I tried to fix the right arrow with → with the following result:

2H2 + O2 → H2O

which isn't rendered quite right in my browser (IE 6.0)—the arrow is on the baseline instead of "hyphen height". (The problem seems to be that the arrow is centered vertically on the whole line, which is pulled down by the subscripts. For example, H→O does look right.) Finally, I have decided to switch to TeX markup

2\,\mbox{H}_2+\mbox{O}_2\to2\,\mbox{H}_2\mbox{O}

in the hope that this satisfies everybody.
Herbee 21:31, 2004 Mar 3 (UTC)

I love how the formula for thermite is on this page. Mayhaps an explosive should not be used as an example. miles32

It is explosive. :) Other reactions common in textbooks, such as H2 + O2 -> H2O are more likely to be explosive. Itub 02:27, 16 January 2007 (UTC)

Should there be H2 + O2 -> H2O + O2 Giving the other product O2?

Nah the balanced equation is 2H2 + O2 -> 2H2O. Bsimmons666 (talk) 19:03, 18 October 2008 (UTC)

Merger proposal[edit]

All these articles (Stoichiometry,Stoichiometric coefficient,Gas stoichiometry)are related to the same concept and would be better if they are accessible on a single page. It will help by providing a better understanding of the article and save some trouble for a person new to the concept. Myth (Talk) 21:00, 28 January 2007 (UTC)

I Believe that the links included in the See Also section should be enough... both subjects are prone to grow up enough to keep their own pages... —Preceding unsigned comment added by Paulo.maia (talkcontribs) 06:57, 26 March 2007

they should go together. 'nuff said. —Preceding unsigned comment added by 67.84.0.201 (talk)

They should be merged until it is true that they have grown and developed enough information to merit their own space in separate articles. --Antonio.sierra 01:32, 6 September 2007 (UTC)

Added a short section on the stoichiometry matrix. --hsauro 08 Oct 2007

Counting[edit]

I might just suck at counting, but I believe in "Different stoichiometries in competing reactions" there is an extra Hydrogen. Well actually it's an extra n hydrogens, but I think people get it... WAIT!!! that does say 6-n... hm... LIMEY 07:09, 2 December 2007 (UTC)

Addition[edit]

This article needs to mention something about Job's method. —Preceding unsigned comment added by 204.8.12.66 (talk) 15:16, 9 January 2008 (UTC)

In the section Stoichiometric Air/Fuel Ratios of Common Fuels, the mass percent numbers have been calculated incorrectly. For example, for ethanol, the mass ratio is given as 9 to 1 and the mass percent as .11111 which is 1/9. The total mass for this case should be 9+1=10, and then the percent fuel is 1/10 = 10%. This error is consistent for all the fuels. Jpittot (talk) 20:21, 30 January 2008 (UTC)

Is this correct?[edit]

The article says, "the units of grams form a multiplicative identity, which is equivalent to one (g/g=1), with the resulting amount of moles (the unit that was needed), is shown in the following equation,

\left(\frac{2.00 \mbox{ g NaCl}}{1}\right)\left(\frac{1 \mbox{ mol NaCl}}{58.44 \mbox{ g NaCl}}\right) = 0.034\ mol"

however it leaves out the NaCl at the end. Shouldn't it be still there as there are two "NaCl" in the numerator while there is one "NaCl"in the denominator,

\left(\frac{2.00 \mbox{ g NaCl}}{1}\right)\left(\frac{1 \mbox{ mol NaCl}}{58.44 \mbox{ g NaCl}}\right) = 0.034\ mol \mbox{ NaCl}

(Unless, of course, that italicized "mol" means you don't have to, i dunno...)Electric durian (talk) 07:10, 20 September 2008 (UTC)

Where is composition stoichiometry?[edit]

Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry

Well now then shouldn't "composition stoichiometry" have a page or at least some definition. —Preceding unsigned comment added by 134.131.125.50 (talk) 21:36, 22 October 2008 (UTC)

Agree Logan Talk Contributions 23:13, 3 February 2010 (UTC)

Explain the practical side[edit]

The article is too centered on the theoretical calculations, which makes it difficult to understand to someone not previously knowing the subject. It should also explain how the experiments are performed and how the "amount of products that can be produced" is measured in practice (not just as the result of a previously defined formula). That is, explain the basis of the technique instead of only the way it's used. Diego (talk) 15:26, 5 January 2010 (UTC)

OH YES IT IS!!!! —Preceding unsigned comment added by 75.23.222.214 (talk) 00:44, 15 January 2010 (UTC)

Non-technical intro[edit]

I've rewritten the intro to make it less technical and hopefully less daunting for the non-technical reader. Almost all the original text from the previous version has been kept, but I've rearranged it to bring the example forward and improve the flow of ideas. Also, I've explicitly defined both reaction and composition stoichiometry, as the wiki link in the previous version to composition stoichiometry didn't work (a page on composition stoichiometry may never have existed).

Chemists, help me out here! I'm hoping with a bit more work, we can get rid of the "too technical" tag that has been placed on the article. Pls review the examples and definitions for accuracy. Also needed are some definitional references to good chemistry textbooks for the various terms defined (I don't have access to any chem textbooks at the moment, and most of the web-based definitions aren't from clearly authoritative sources). Ross Fraser (talk) 00:29, 19 July 2010 (UTC)

Error of sign[edit]

In the section defining the stoichiometric coefficient, there are sign errors. "CH4 + 2 O2 → CO2 + 2 H2O, the stoichiometric coefficient of CH4 would be 1 and the stoichiometric coefficient of O2 would be 2."

According to the definition of the "stoichiometric number" by IUPAC, the sign (consumption or production) is included in the coefficient. So in the example the stoichiometric coefficient of CH4 would be -1 and the stoichiometric coefficient of O2 would be -2. http://www.iupac.org/goldbook/S06025.pdf Nicolas Le Novere (talk) 16:19, 17 September 2010 (UTC)

dimensionless[edit]

The paragraph starting with "The (dimensionless) "units" may be taken to be molecules or moles. " does not make sense. Stoichiometric numbers are dimensionless because in the current interpretation of reaction kinetics, they represent the substance consumed/produced relative to an hypothetical substance which stoichiometric number would be 1. Another way of saying that is they represent the number of moles/molecules transformed per number of moles/molecules of reaction events. Because it is mole/mole or molecule/molecule, the result is dimensionless. It may not be taken as to be anything. dimensionless is dimensionless. We are talking of the dimensions of the SI units here. mole/mole = second/second = meter/meter = kg/kg. Nicolas Le Novere (talk) 16:19, 17 September 2010 (UTC)

What happened to the 'Definition' section?[edit]

In earlier versions there was a section called Definition, that elaborated on the basic concepts. Was it deliberately removed or did it get lost in the wiki cut-n-paste process? I'm restating it into the article, since it seems to have been lost to vandalism. Diego Moya (talk) 13:23, 30 October 2010 (UTC)

Error in Stoichiometric Air Fuel Ratios[edit]

There is an error in the mass ratio of air/natural gas for stoichiometric combustion. The ratio is listed as 14.5. Since NG is mostly methane, the ratio should be closer to 17.2 (the correct methane/air mass ratio). Since the table does not give the exact composition of (for example) NG or gasoline, and both of these substances have variable composition, it would be better to cite the NG and gasoline composition for which these ratios are stated. 71.136.237.55 (talk) 20:31, 4 July 2011 (UTC)

Composition Stoichiometry example in intro makes no sense[edit]

"1 mol of ammonia consists of 1 mol of nitrogen and 3 mol of hydrogen. As the nitrogen atom is about 14 times heavier than the hydrogen atom, the mass ratio is 14:3, thus 1 kg of ammonia contains 176 g of hydrogen." -- this makes no sense: it would only be true of 1 mol of ammonia consisted of 1 mol of nitrogen and 1 mol of hydrogen. But there are *3* mols of hydrogen! Unless someone can explain otherwise, I'll re-write this example. --Ross Fraser (talk) 00:34, 21 March 2012 (UTC)

Please don't make corrections based on your personal knowledge, unless you've actually studied chemistry, let alone stoichiometry at this elementary level. The example was referring to the Haber process, and funnily enough it was also wrong, as well as your correction. 1 mol of nitrogen and 3 mol of hydrogen result in 2 mol of ammonia. Remember that hydrogen and nitrogen are also diatomic. Rifasj123 (talk) 06:08, 25 September 2013 (UTC)

Stoichiometry matrix extension to nuclear transformations[edit]

How is the stoichiometry matrix extended when nuclear transformations (alpha and beta-decay, nuclear reactions, etc) must be considered? It would be useful to add some details.--188.26.22.131 (talk) 11:04, 26 August 2013 (UTC)

Poor quality[edit]

To be honest the quality of this article is abysmal. Its scope is at a high school level, and it seems more suited as a tutorial rather than an encyclopedic page.

If I have time I will make major changes, but hopefully someone with a high degree of knowledge in Chemistry can help improve this article. It only explains topics in the context of solving elementary chemistry problems, and doesn't really elaborate on their interrelation, and relevance to the field of stoichiometry itself. Additionally a historical component could also be beneficial.

But in my opinion the most appalling issue with this article is the lack of citations, and thereby credibility on the subject matter. Rifasj123 (talk) 02:52, 24 September 2013 (UTC)

Wrong volumetric AFR for diesel[edit]

All other values in the table are given as air-to-fuel (AFR) volume ratios. If this is also the volumetric-AFR for diesel is clearly wrong. Probably that this is the fuel-to-air volumetric ratio instead - but i wouldn't like to assume. Either way, the table is confusing without explicit headings. — Preceding unsigned comment added by 85.211.37.96 (talk) 11:04, 5 January 2014 (UTC)

Yes, 0.094 volumes (or moles) of air for 1 volume (or mole) of diesel is absurd. The revision history of this article shows that the value 0.094:1 was not in the initial table, but was added on 16 Nov 2009 by editor 71.112.167.243 who has not contributed subsequently. Since we cannot contact him/her to check the source, I will just remove the incorrect value.
As for the headings, the article section in November 2009 had a more explicit title including the words air-to-fuel. I will restore this title to make it clear that the whole table refers to air-to-fuel ratios (except possibly the 0.094). Dirac66 (talk) 14:33, 5 January 2014 (UTC)