Talk:Enthalpy change of solution
|WikiProject Physics||(Rated Start-class, Mid-importance)|
|WikiProject Chemistry||(Rated Start-class, Low-importance)|
Positive vs. Negative
Am I correct in thinking that a compound with a positive heat of solution will produce a cooling effect when it is dissolved in water, and vice-versa? This article seems to support that (eg. ammonium nitrate has a substantial cooling effect; it has a positive enthalpy of solution), but if this is true, then several articles (erythritol, isomalt, and probably others) and a patent (http://www.freepatentsonline.com/20050196517.html) contain glaring errors. --Pyrochem 03:09, 11 September 2007 (UTC)
Hi, sodium chloride dissolved in water, has +3.89 kJ not kcal per mol, I'll change tat (data source, google, wiki german, and so on) —Preceding unsigned comment added by 126.96.36.199 (talk) 21:47, 14 January 2009 (UTC)
Since this is a scientific page and scientists havnt used calories for year the given values should really be in kJ/Mol, I wont take the desision upon myself but I deffinetly support the change —Preceding unsigned comment added by 188.8.131.52 (talk) 08:28, 25 March 2009 (UTC)
Values at interim solution points
The table gives values for the full range of dilution from infinitely concentrated to infinitely diluted, which is fair enough. A description of how the delta-H changes over the range would be useful here. For example: what is the heat given off when 10N HCl is diluted to 1N HCl ? (talk) 05:41, 13 Feb 2011 (UTC)
Negative Enthalpy Change error
"Solutions with negative enthalpy changes of solution form stronger bonds and have lower vapor pressure."
Is in the article.
If a solution had a negative enthalpy change then it is exothermic. Thus it broke bonds of a higher value and formed bonds of a lower value, giving the difference off as heat. Ergo the bonds it forms will be weaker, correct? —Preceding unsigned comment added by 184.108.40.206 (talk) 11:39, 9 May 2011 (UTC)
No, because the bond breaking step is endothermic, and the bond making is exothermic, so the bond making step must have a bigger energy difference to give an overall negative enthalpy of solution. The bonds made are therefore 'stronger' Skihatboatbike (talk) 19:08, 11 March 2012 (UTC)
Comment about bond strength and vapour pressure
Hi folks, I removed this as it seemed to be without context or point of reference - the stronger bonds part of it was without reference, and the vapour pressure seemed more relevant to talk of gases which was not the specific topic in this section - all the values given in the table are for solids.Skihatboatbike (talk) 19:49, 11 March 2012 (UTC)