Talk:Activity (chemistry)

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I don't understand why this redirected to the disambiguation page. I've fixed it and tried to write a bit of an article from other sources on the net, but I'm only here because I was looking for information, and I'm not an expert on the topic. Please, chemists, help me!!!

Contents

[edit] Unit; examples

What's the unit for measuring activity (I'm assuming it's unitless)? Could we find an example of a numerical value of a common solution?

Do the activities of all the components of a mixture add up to one?

The article currently fails to give a usable definition of the term.

RandomP 16:38, 19 September 2006 (UTC)

Interestingly, the definitions in the German and English articles describe a different quantity. As I know it, activity is unitless, but defined against an arbitrary standard 1 mol dm-3. Therefore, a concentration of 1.0 mol dm-3 and a coefficient of 0.9 gives an activity of 0.9. --Vuo 21:35, 19 September 2006 (UTC)
Thanks! Do you have any examples that involve specific solutions that might be well-known?
"unitless, but defined against an arbitrary standard", at least to me, appears to make no sense whatsoever. A concentration of 1 mol/l and a coefficient of .9 should surely give an activity of .9?
not really suggesting doing anything, yet, but in the interest of the sanity of any high school students who might not be allowed the same sloppiness with units in their science classes, I'd like to see sloppy use of units clearly marked on WP, I guess ...
RandomP 21:46, 19 September 2006 (UTC)
Actually, the French article seems to have a lot of good content. --Vuo 22:51, 19 September 2006 (UTC)
The activity in Chemistry is one of the few units which doesn't have a unit. So this is completely normal(It's because when you divide mol.L-1 with mol.L-1 the result has no unit).

[edit] Usable definition, exact as it was defined

  • Original Lewis' definition is:
a_i = \frac{f_i}{f^{o}_i}

so ratio of fugacities. DEfinition is valid for SOLIDS, LIQUIDES and GASES (not only for gases)!! You can choose denominator (reference fugacity) arbitrarily !! (only the usage is 101325 as perfect gas for gasses, and fugacity of pure component for solids)

  • Lewis definition of fugacity is:
d\mu_i = RT d\ ln(f_i)
  • LInk both equetion we get:
\mu_i - \mu^{o}_i= RT \ln {\frac{f_i}{f^{0}_i}} = RT \ln {a_i} —Preceding unsigned comment added by 212.5.210.202 (talk) 10:34, 25 September 2007 (UTC)

[edit] Merger/Translation

Obviously the french and german articals cannot be merged without translation. If users who speak french or german or preferrably both could judge which is best it could be requested that that article be translated and merged with the english article. Vuo Has already suggested that the French article has a lot of good content what are others peoples views and it could then be requested for translation from whichever comes out on top. --Ksbrown 21:03, 22 September 2006 (UTC)

I have added it to the french translation board: Wikipedia:Translation_into_English/French#:Activit.C3.A9_chimique Ksbrown 15:39, 23 October 2006 (UTC)
The french article was merged with the english article and no original information from the english article was lost. The translation was done by SamiKaero. -Ksbrown 17:04, 24 October 2006 (UTC)

[edit] Merger proposal

Hello,

I came across Activity coefficient, and felt that this article does a significantly better job of covering the topic and propose that what is good from that article be merged here, but not by me! Thanks User A1 (talk) 13:38, 22 December 2007 (UTC)

Thanks for this proposal. I was unaware of the existence of Activity coefficient when I re-vamped this article. Obviously that article is more comprehensive. What, if anything, do you think should be kept from this one?
I'm not an expert at merging, so I'm worried about the Wiki citations to the two articles being correctly processed.Petergans (talk) 10:22, 31 December 2007 (UTC)
Perhaps both articles are needed because it it a vast area. My understanding was that the article on activity coefficient will focus on how to practically calculate the activity coefficients in the specific cases, and not dwell on what activity is. This is similar to the situation in articles "equilibrium"-"equilibrium constant", "heat transfer"-"heat transfer coefficient", and numerous others. Just my C$0.02. Stan J. Klimas (talk) 14:40, 16 February 2008 (UTC)

[edit] P*solvent and Ksolute

Hi. Would it be possible for somebody to write explicitly what P*solvent and Ksolute in section "definition" are? Thanks!