User talk:Powertoold

Solubility Equilibrium
You are correct in your comment. I will fix that paragraph tonight (unless you do it first), once I can find a confirming reference. Karl Hahn (T) (C) 20:50, 23 May 2007 (UTC)


 * I have fixed the paragraph in question. Have a look, then feel free to post a comment on the change on my talk page. Karl Hahn (T) (C) 01:12, 24 May 2007 (UTC)


 * In response to your latest comment, here is the quotation from General Chemistry by Linus Pauling: "If the partial molar enthalpy of solution of the substance (the change in enthalpy when one mole of the crystalline substance is dissolved in a very large amount of nearly saturated solution at constant temperature and pressure) is positive, then solubility increases with increasing temperature, and if it is negative the solubility decreases. This is, of course, in agreement with Le Chatelier's principle." It also gives a good example of both cases, which is sodium sulfate. Below 32°C, the decahydrate exists, whose enthalpy of solution is positive (endothermic). The graph in the book shows the solubility curve sloping up in that range. But above 32°C, the crystal phase is the anhydride, whose enthalpy of solution is negative (exothermic), and in that region the graph slopes down. Karl Hahn (T) (C) 02:36, 24 May 2007 (UTC)