Talk:Rate equation

From Wikipedia, the free encyclopedia

This article is within the scope of WikiProject Chemistry, which collaborates on Chemistry and related subjects on Wikipedia. To participate, help improve this article or visit the project page for details on the project.

???	This article has not received a rating yet on the quality scale.
???	This article has not received a rating yet on the importance scale.

I've updated the page to include zero-order rate laws so there is an explanation of what they are instead of just being implied. I've also rearranged some of the formula's, most notably the second order AB integrated rate law, which is now in an exponential form. I've also removed the subscript t's associated with the concentrations in the integrated laws. Many textbooks leave out the subscripts, and it looks neater without them, however, if it becomes confusing, perhaps they should be reincluded?--Artorius 11:17, 3 Jun 2005 (UTC)

1 Requested Move
2 Closed system assumption
3 Explanation?
4 Second-Order Example Not Possible

[edit] Requested Move

It seems that there are a few pages that already explain reaction rates in chemical reactions. This being one of them, another being the page called Chemical Reactions and the third being reaction rate. Both this article and the article discussing reaction rates can be easily trimmed down and merged into the Chemistry article. I do not have the understanding or ability to move so much information so I'd appreciate it if someone considered doing so. Aznph8playa 00:26, 30 May 2005 (UTC)

this page will get extented to include pseudo first order reactions and steady state etc (much more out there). The chemical reaction page should be as broad as possible (which it is not at the moment) and is now in need of attention (missing: biochemistry, electrochemisty, organometallic chemisty, inorganic chemistry). Reaction rates and rate laws are also not the same. Please consult the Wiki guidelines, this is the encyclopedia part, what you have in mind really belongs in wikibooks rikXL 15:44, 30 May 2005 (UTC)
- Ah my mistake. It seems I haven't taken enough chemistry. I had thought there wasn't much more past the three rate laws: zero, first and second. Thanks for the clearification. Aznph8playa 19:16, 30 May 2005 (UTC)

[edit] Closed system assumption

I think it is unfortunate that most texts (chemical textbooks as well as wiki texts) that try to explain reaction rates, rate laws etc. confuse rate law with the result of a mass balance for a closed system. I've tried bringing some clarity to this issue under mass balance but the more I look through wikipedia the more problems I find.

Consider for example a bathtub in which we have some bathing salt dissolved. If we fill in more water, the concentration will decrease. With the definition of rate law commonly used by non-chemical engineers many people will (trust me on this) misunderstand the system and think there is a reaction going on since $\frac{dC}{dt} \neq 0$ . But $\frac{dC}{dt}$ does not define reaction rate! One must first write down a mass balance before a link between $\frac{dC}{dt}$ and the reaction rate can be found! Saittam 15:52, 12 August 2005

I guess it is up to us to strike a balance between chemists and chemical engineers view on reaction rates. Wiki should not respect the classical boundaries and there should not be two separate chemical kinetics articles for each group . The way you have included the mass balance link in rate law is the best way to do this. I may also help to use the bathtub example in the text itself and not just in talk because it really brings home your point. V8rik 20:59, 15 August 2005 (UTC)

[edit] Explanation?

Shouldn't there be an explanation of why the rate law works? I understand that a lot of scientific articles don't have an explanation section, but in those cases the explanation is either unknown, obvious, or exceedingly complex; the explanation for this law isn't any of those. Comments before I add it?

The reason that a rate law "works" is that it is simply a description of what one "sees"; it can be used to test hypotheses of a reaction mechanism, that is true, but not all rate laws are completely explained. Physchim62 (talk) 16:20, 15 December 2005 (UTC)

or do you mean how to derive the rate laws? just make the edit you have in mind, I am intrigued V8rik 20:22, 15 December 2005 (UTC)

[edit] Second-Order Example Not Possible

The example second-order reaction $\left(2\mbox{NO}_2 \rarr{} 2\mbox{NO}_2 + \mbox{O}_2\right)$ isn't possible; perhaps $\left(2\mbox{NO}_3 \rarr{} 2\mbox{NO}_2 + \mbox{O}_2\right)$ was intended? --Shadypalm88 06:34, 6 February 2006 (UTC)

According to these lecture notes, it seems that $2\mbox{NO}_2 \rarr{} 2\mbox{NO} + \mbox{O}_2$ was the intended equation. I have made this change and also cleaned up the LaTeX a little. --Shadypalm88 06:34, 6 February 2006 (UTC)