Talk:Van 't Hoff equation

Peer review and responses during the educational assignment in Fall 2013

Peer Review 1

Mr.Holmium (talk) 17:29, 2 November 2013 (UTC)Mr.Holmium

Content

The introduction is very concise and to-the-point. Its simplicity seems appropriate for the general public. It's also nice that a statement regarding the van't Hoff equation's utility is included. The length of each section is appropriate and the content is explained well and is not duplicative of the content already on Wikipedia. Compared to the current site, the content about the equation’s derivation is better organized in this edited version. I’d suggest label which equation is the van’t Hoff equation (e.g. the differentiated equation or the one highlighted in green?) because it would be very helpful to reference back to it later in the sections dealing with the van’t Hoff plot. Each important concepts of the page is linked to their respective Wikipedia page for further reference. Though, the term “isotherm” can be linked to the Wikipedia page “Isothermal process” because the content of “Van’t Hoff isotherm” doesn’t explain/relate to the term clearly. Also, it would be helpful to have a sentence relating the similarity of the van’t Hoff isotherm equation with the one under standard condition. For example, relating RT ln Q with RT ln K_eq. The subsection “Van’t Hoff Plot” has a very good coverage. It’s very precise and detailed enough for an encyclopedia page. I’d suggest referencing which equation you’re analyzing (as mentioned above) because the green highlighted equation in the derivation is not the one used for the plot. The examples used for analyzing the endothermic and exothermic reactions seem appropriate and show the utility of the van’t Hoff plot. One thing missing here is the relevance of entropy. Do people care about entropy? If not, is it because the change is insignificant?

Figures

The figures seem like they’re made by the authors editing the page, thus they’re original. They’re simple and descriptive, thus they’re of good quality and support the text appropriately. The only thing I would change in the figure is use subscript for “eq” in “ln K_eq.”

References

The references are complete and have a good balance between non-journal and journal sources. Though, some information can be referenced to non-journal sources so that they can be accessible to the public. For example, the temperature dependence of the van’t Hoff plot can be referenced to a university page that has information about it (http://tyr0.chem.wsu.edu/~kipeters/Chem331//T-depend-lnK.pdf).

Overall presentation

Overall, the page is very well done and expanded compared to the current site. The amount of information and figure is enough and explained in good details. There are only a few things that can be improved:

• Better clarification in the Van’t Hoff Plot section: reference to equation, a statement about entropy.
• When analyzing the temperature dependence, I’d suggest write a note that as T increases, 1/T decreases, therefore higher T’s lie at the left of the plot. This is very obvious but sometimes people forget that the plot is a function of 1/T.
• I’d suggest make a new section (section 3 on “Applications” perhaps) for the van’t Hoff analysis and mechanism study because these two are about applications of the van’t Hoff plot. The “temperature dependence of the van’t Hoff equation” seems appropriate under the “Van’t Hoff Plot” section.

Peer Review 2

Educatefreechemistry (talk)

Content

The introduction is easy to understand and the addition of the application of van’t Hoff equation is very helpful for all users in general. Users are always more likely to look for the application of the topic at the beginning of the page. Length for all the sections except for van’t Hoff analysis is very justifiable. It would be a good idea to talk about biological application in brief. There is a lot of application of van’t Hoff factor in biology or biochemistry. Adding paragraph or an example from that section might make this page more interesting and informative. All the equations added by the user seem to be original and good quality. It might be a good idea to use Keq instead of just K as equilibrium constant. There are enough equations in the page to explain the topic and derive the formula clearly and step by step. That will make it easier for non-chemistry user to understand the topic as well. Most of the important concepts and terms are linked to the appropriate wikipedia page.

Figures

The figures are well made and explain the concept in the page clearly. They are easy to read and high quality. Being consistent with the spaces in the formula of slope and interception might make it better. I think using a picture in the middle of the page (or side of the page) instead of just a thumb will be more users friendly. The thumb will force the user to open a new page just to enlarge a picture which is time consuming. Other than that, the figures are nice and informative enough for the page. Also, rewriting the linear form of the equation again in either endothermic reactions and exothermic reactions section or their plot will make sure that the user know exactly what equation the plot corresponds.

References

The references are diverse containing journal articles and books in good distribution. Reference 7 (website) cannot be opened from off campus. So, it would be a good idea to fix that issue or remove the reference. Including few journals of biological implication of Van’t Hoff factor might be a good choice.

Overall Presentation

The page is concise but well explained. It is easy to follow even if the user is non-expert. The derivation of equations are very clear and organized. It might be a good idea to change few things in the figures as suggested above. Also, adding brief explanation on the application of van’t Hoff equation and plot might make the page better and complete.

Additional Comments

UMChemProfessor (talk) 01:43, 5 November 2013 (UTC) It might be nice to provide some context for the values that are obtained for enthalpies and entropies. You could accomplish this by providing specific examples, or linking to other Wikipedia pages where the van't Hoff analysis was used and interpreted. The "mechanism study" section should probably be titled "mechanistic studies". The peer reviewers have made some good suggestions. I would like to add that your figures should be larger. They are too small to read without clicking on them to enhance.

Suggestions from ChemLibrarian (talk) 15:43, 5 November 2013 (UTC)

1. As other reviewers suggested, you need to adjust the image sizes and location. See this page Wikipedia:Picture tutorial for how to place the image at different places and adjust the size.
2. This sentence in the introductory paragraph could use a citation "It was proposed by Dutch chemist J.H. van 't Hoff in 1884" .

Response to reviewers

Thank you for taking the time to look over our site and offer suggestions. They were very helpful and we attempted to follow all of them. We re-sized our figures so they are easier to read without having to expand them. We also made sure we consistently used K_eq in our text and figures. We removed the reference that couldn't be opened, as it was not really needed. We also added the citation that was need in our introduction section. In the section about the van't Hoff equation, we changed some of the wording to make it clearer which equations were which, and we repeated the linear form of the equation in our section about van't Hoff plots so it was clear which version was being used. We also tried to make the van't Hoff isotherm section easier to understand. We added a specific section on applications of the van't Hoff plot to separate the explanation from our examples. Finally, we added a specific example of a van't Hoff analysis to demonstrate the kinds of numbers that can be obtained from this type of analysis and to show a biochemical application of the van't Hoff plot. Sjsteiner77 (talk) 21:13, 10 November 2013 (UTC)

Pressure

Hrm. So I was in chemistry and i was thinking. Pressure changes should affect things exactly the same way as temperature changes...so does a equation like the van't hoff equation exist for pressure changes as well? (in gases only, i'm guessing)

our professor tells us to use PV=nRT to calculate, assuming Kc is the same for both pressures. However, I can't see how this is possible!

Strangely enough, RICHARD C. TOLMAN; “Equilibria in dispersed systems and the thermodynamic theory of theory of colloids”; Journal of the American Chemical Society; American Chemical Society; April 1913; 35 (4): pp. 317–333. actually refers to "PV=nRT" as "the law of van't Hoff".

—DIV (128.250.80.15 (talk) 06:11, 31 March 2008 (UTC))

The equilibrium constant K does not depend on pressure !

Since it's defined at equilibrium where DG = 0, we have

DG = DGo + R.T.ln K

so ln K = - DGo/R.T , it depends on DGo, at a standard state

defined at 1bar (constant pressure)

Note that the composition at equilibrium (Kx) can

depend on pressure but not the above defined K —Preceding ::unsigned comment added by ::201.11.138.212 ([[User ::talk:201.11.138.212|talk]]) 21:14, 29 May 2008 (UTC)

Please see Equilibrium_constant#Pressure_dependence. Best regards, Stan J. Klimas (talk) 23:27, 29 May 2008 (UTC)

Arrhenius

Main page should probably mention or refer to Arrhenius.

Empirical Importance

It should be mentioned that van't Hoff equation was very important in the non calorimetric determination of DHo and DSo from plots of ln K x (1/T) adjusting a curve (most times approximated as a line when DHo ~ constant) to empirical data of K at different temperatures. Edgardo. —Preceding unsigned comment added by 201.11.138.212 (talk) 21:20, 29 May 2008 (UTC)

Equation

Could I request a review of the linear form of the equation? I believe it should be (1/T1 - 1/T2), not the other way around. — Preceding unsigned comment added by 72.94.158.91 (talk) 03:28, 13 January 2012 (UTC)

Late answer - that is why there is a minus sign in front of the right-hand-side. With the minus sign it is (1/T2 - 1/T1) as in the article; without the minus sign it would be (1/T1 - 1/T2) as you say. The two are equivalent and some books do it one way and some the other. Dirac66 (talk) 00:11, 18 March 2013 (UTC)

Approximate???

In practice, the equation is experimentally approximate in that both enthalpy and entropy changes of a process (reaction) vary (each differently) with temperature.

It's still exact, right? It's just that delta-H in the equation changes with temperature. AlphaHelical (talk) 22:25, 3 May 2013 (UTC)

You are correct. The equation with ΔH as a function of T is exact and can be rigourously derived from the laws of thermodynamics. If ΔH is assumed constant, then the equation becomes approximate although it is easier to work with. These points could be made more clearly in the article. Dirac66 (talk) 01:29, 4 May 2013 (UTC)

I have clarified this now. Dirac66 (talk) 20:22, 21 April 2014 (UTC)

Vukancic-Vukovic equation

I think it is time to stop deleting this alternate name, since several sources have been given in the recent scientific literature to show that it really is sometimes used. Even if (English-language) physical chemistry textbooks only mention van't Hoff.

Now it would be useful to know more about Vukancic and Vukovic. Who were they, what were their first names, where did they work? More important: when did they propose their equation and how did their version compare with that of van't Hoff? Perhaps we could think of adding a History section mentioning van't Hoff and also Vukancic and Vukovic. Dirac66 (talk) 02:11, 27 October 2016 (UTC)

As far as I can tell, and as was pointed out by a recent editor, this appears to have been a self-promoting piece of vandalism. As the editor mentioned, this equation has only been referred to this way in articles (and only articles in relatively obscure journals) published since the names were added to the page back in 2010. There are no older references, as I have confirmed preliminarily using Google Scholar (https://scholar.google.com/scholar?hl=en&as_sdt=0%2C31&q=Vukancic+and+Vukovic&btnG=) and could easily confirm further through a library search if needed. In other words, a number of people who really should have known better appear to have been taken in by a Wikipedia-abetted hoax. KeeYou Flib (talk) 19:22, 23 April 2021 (UTC)

Let's discuss. In order for this "new name" to be on the article, its history has to be established. It's not enough to put in hyperlinks to 2-3 articles where the name is used. Who are these people? Why should their names be attached to the equation? What field(s) or nations refer to the equation with this name? More context is needed, please bring it here instead of just adding it to the page over and over. Qflib, aka KeeYou Flib (talk) 22:07, 14 April 2023 (UTC)

van 't Hoff or Van 't Hoff?

Normally, van is not capitalized (unless you're beginning a sentence). The Dutch article doesn't. Samer (talk) 22:22, 3 December 2017 (UTC)

You're right. The correct way is "van 't Hoff". I think the entire page should be updated. Somerandomuser (talk) 23:01, 24 April 2018 (UTC)

I have made corrections to the Wikipedia article. Somerandomuser (talk) 23:37, 24 April 2018 (UTC)

But the first appearance of "van't Hoff equation" (not counting the title) still capitalizes V. Is it some kind of rule?--Runningwolf2 (talk) 23:59, 10 May 2019 (UTC)

What does Ir mean in the equation in the green square?

--Runningwolf2 (talk) 23:59, 10 May 2019 (UTC)

• I don't see Ir. If you are referring to ln, it means natural logarithm. I'll mention that in the article. Dirac66 (talk) 00:54, 11 May 2019 (UTC)

The needs-references error propagation section

After scratching my head a bit, this section seems to be using a lot of words and maths to say that Propagation_of_uncertainty can be important. Would a short note to this effect be more useful than a detailed worked example?

As an aside, I think it would be useful to reinstate something similar to the section deleted when this section was created, because the explanation of qualitative visual assessment of the plot is quite intuitive. Last version was here, I think: https://en.wikipedia.org/w/index.php?title=Van_%27t_Hoff_equation&oldid=628067216#Temperature_dependence_of_the_equilibrium_constant Latrissium (talk) 12:02, 17 May 2019 (UTC)

Absolutely agree with you. I'll turn my hand to that next. KeeYou Flib (talk) 19:14, 21 April 2021 (UTC)

I edited the error propagation section; I think that it works better now. Will work on your other suggestions soon. KeeYou Flib (talk) 19:53, 23 April 2021 (UTC)