Talk:Debye–Hückel theory

Raoult's Law vs. Henry's Law

I tried to fix this, but someone reverted my edits, so let's have at it here.

Raoult's Law (more properly the Lewis-Randall Rule) is the ideal solution limit that applies to solvents: the base case is the molecule surrounded by itself. This is the usual standard state chosen for solvents.

Henry's Law is the ideal limit that applies to solutes: the base case is the molecule surrounded by solvent molecules, unable to "see" other solutes.

The Debye-Hueckel theory applies to solvated ions, which do not exist as pure components. The Henry's Law limit is therefore applicable.

With respect to Petergans's comment about applying to gases: Henry's Law describes the equilibrium between an ideal (infinitely dilute) solute in equilibrium with an ideal gas mixture. Raoult's Law, similarly, describes the equilibrium between an ideal (nearly pure) solvent in equilibrium with an ideal gas mixture. Deviations from Henry's Law are what is relevant to the Debye-Hueckel limiting law; it doesn't make sense to talk about Raoult's Law for ions. Kaiserkarl13 (talk) 13:41, 19 April 2021 (UTC)

Thanks for this clarification. Both laws must apply for sufficiently dilute solutions. Petergans (talk) 08:09, 20 April 2021 (UTC)

Not so. Raoult's Law specifically refers to the fugacity of the pure component (approximately equal to the saturation pressure) being the proportionality constant, while Henry's Law refers to the slope of the fugacity of the infinitely-dilute solution. The Raoult's Law limit applies in the limit of an infinitely concentrated solution (e.g., a mole fraction of 0.999 in pure water). The Henry's Law limit applies in the limit of an infinitely dilute solution (e.g., a mole fraction of 0.001 in a particular solvent). Only in solutions that are actually ideal solutions throughout the entire range (i.e., where the activity coefficients are identically 1 everywhere) are the two equivalent. Kaiserkarl13 (talk) 02:46, 23 April 2021 (UTC)

Link to apparent quantities of components in electrolyte solutions

I have encountered a source mentioning the link with an apparent molar property like volume: http://pubs.rsc.org/-/content/articlelanding/1968/tf/tf9686401898#!divAbstract--5.2.200.163 (talk) 14:48, 11 December 2017 (UTC)

B parameter

In the formula for the B parameter, what is N? — Preceding unsigned comment added by 80.182.41.116 (talk) 15:48, 29 December 2018 (UTC)

N is generally understood to be Avagadro's constant. Petergans (talk) 11:48, 30 December 2018 (UTC)