Talk:Enthalpy change of solution

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)

You are correct. The articles on erythritol and isomalt are also correct. I haven't had time to read through the patent though. Iggwilv (talk) 03:25, 15 April 2010 (UTC)

Sodium Chloride
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 77.239.33.181 (talk) 21:47, 14 January 2009 (UTC)

Sodium Hydroxide
what is value for sodium hydroxide? —Preceding unsigned comment added by 153.47.0.76 (talk) 10:22, 10 March 2009 (UTC)

I've added the value for NaOH. It's -44.51 kJ/mol in water at 25°C. --Iggwilv (talk) 17:06, 15 April 2010 (UTC)

SI units
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 203.221.197.173 (talk) 08:28, 25 March 2009 (UTC)

The SI unit is kJ/mol. Small letter is used for m.129.94.222.43 (talk) 05:37, 26 March 2010 (UTC)

I'm going ahead and making these changes since nobody has objected. User:Iggwilv (talk) 02:58, 15 April 2010 (UTC)

Chemistry/Physics
Since this is a topic in physical chemistry, I propose that this article be placed in the Chemistry WikiProject instead of the Physics one. Iggwilv (talk) 17:28, 15 April 2010 (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 132.234.214.53 (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)

Dependence on the nature of the solution
The phrase "the enthalpy of dissolution of nonelectrolytes has the value of the enthalpy of fusion or vaporisation" is completely incorrect. It is astonishing that it has been around as long as it has. 130.68.21.160 (talk) 19:03, 13 May 2024 (UTC)