Talk:Ideal solution

Merge

I would like to propose merging this article and Ideal mixture. The two articles appear to cover very similar topics.--GregRM 16:55, 2 February 2007 (UTC)

sloppy math

"The vapor phase is an ideal gas so:

$\ \mu _{i(s)}=\mu _{i(g,pure)}+RTlnP_{i}$"

This equation is wrong because it is not dimensionally consistent. The chemical potential has dimensions of energy per particle, while RT ln of pressure has units of energy per particle times log of pressure. Obviously, the quantity in the logarithm is meant to be normalized by either the total pressure or some standard pressure, perhaps 1 bar. As written, the equation can't be correct. —Preceding unsigned comment added by ChrisChiasson (talk • contribs) 22:57, 8 September 2007 (UTC)

It is correct. The dimensions of chemical potential are energy per particle. The dimensions of R are energy per particle divided by temperature. When multiplied by the temperature the term RT yeilds energy per particle and is consistent with the dimensions of chemical potential. The log term is normalized as you said and has no units. A correction might be to explicitly show division by 1 bar for the normalization.

Just because people understand to use the equation differently that it is written does not make the equation correct. Also, the required normalization is dependent on the standard pressure which has been absorbed into the ideal chemical potential term. It is probably 1 bar in many cases, but it would be helpful if someone could come up with something authoritative and hopefully comprehensive. (a derivation of the ideal chemical potential term would be instructive, ala http://phasediagram.dk/chemical_potentials.htm )ChrisChiasson 07:26, 7 October 2007 (UTC)

The pressures should indeed be relative to standard pressure (1 bar) and omitting $p^{\circ }$ is sloppy. But the more fundamental problem is that the derivation is circular since Raoult's Law is best described as a *consequence* of the chemical potential of a ideal mixture. The chemical potential is itself best explained in terms of the entropy of mixing. 84.92.241.186 (talk) 12:12, 30 December 2007 (UTC)

I added the formal definition section which contains a more formal description of the model. I need help adding wiki links because I'm new to this editing wikipidia.

Since english is not my first lenguage (it's spanish) there may be some misspeled words. Would be great if you could have a look.Utanari (talk) 22:02, 8 September 2008 (UTC)

Rework

Once I got started, it was hard to resist reworking the page. Hopefully the result flows better and fixes the problems above. 84.92.241.186 (talk) 13:31, 30 December 2007 (UTC)

incorrection

In the section consecuences it says that every component of an ideal mix follows Rault's law but that is not completely wright one has to assume the hypothesis that the vapor in equilibrium whith the liquid mixture is formed by ideal gasses. It is true that in practice this is taken for granted in many cases but I think it should be writen in a more precise form.Utanari (talk) 10:29, 9 September 2008 (UTC)

example for non-ideal

friends! ARE water +HCl and water + H2SO4 NON-IDEAL SOLUTIONS? IF SO FORCE OF ATTRACTION BETWEEN UNDISSOCIATED MOLECULES OF HCl [OR H2SO4 IN SECOND CASE]AND WATER HAVE TO BE CONSIDERED.IS THIS UNDERSTANDING CORRECT?I MEAN ,EVEN BEFORE THE ACIDS DISSOCIATE IN TO IONS CONTRACTION IN VOLUME HAPPENS,RIGHT OR WRONG? WHAT HAPPENS IF 10 mL OF WATER IS ADDED TO H2SO4 TAKEN AS SOLVET[SAY 90 mL]? —Preceding unsigned comment added by Sarvodayaharish (talk • contribs) 20:03, 15 November 2008 (UTC)

Temperature range of ideality

Is the ideality of this type of solution maintained over all temperature ranges?--5.2.200.163 (talk) 12:23, 11 July 2016 (UTC)

Not necessarily for real examples of almost ideal solutions. Of course if we postulate an unidentified ideal solution, it is assumed to be ideal at all temperatures. But a real example, say ethane and propane, is only approximately ideal, probably in the temperature range where both components are liquid. And the deviations can be larger at other T, say when one component becomes solid or supercritical. Dirac66 (talk) 19:44, 11 July 2016 (UTC)

Ideality at all temperatures can be called perfect ideality corresponding to a perfectly ideal solution. It is interesting to notice in this context that the electrode potential determinations involves the assumption that the electrode potential of the standard hydrogen electrode involving an ideal solution with hydrogen ion is zero at all temperatures equivalently to standard enthalpy of formation of hydrogen ion is also zero at all temperatures.--5.2.200.163 (talk) 12:35, 25 July 2016 (UTC)

Consequence - corollary

Can an ideal solution exist without obeying Raoult's law?--5.2.200.163 (talk) 12:03, 6 September 2016 (UTC)

The section Formal definition has two alternative definitions, and the answer to your question depends on which definition we choose. If we use the simple definition (as in general chemistry texts) that an ideal solution is one which obeys Raoult's law, then the answer is no, because it would contradict the definition.

However the article says that Some authors therefore define an ideal solution as one for which each component obeys the fugacity analogue of Raoult's law, referring to more advanced thermodynamics texts. With this definition an ideal solution will obey the fugacity analogue of Raoult's law, but not necessarily the original Raoult's law in terms of pressure. Dirac66 (talk) 01:07, 8 September 2016 (UTC)