(Chief Bee)
06-03-04 18:21
No 511239
(Rated as: good read)
Great introductory text about what rules determine the solubility of salts, with several interesting and useful factoids interspersed in a theoretical framework.
The Solubility Rules: Why Are All Acetates Soluble?
William G. Van Der Sluys
J. Chem. Educ. 78, 111-115 (2001) (../rhodium/pdf /solubility.r
Abstract
According to the solubility rules presented in many introductory chemistry texts, all (or most) acetate salts are soluble in aqueous solution. The thermodynamic factors that contribute to the solubility of acetates are compared with those of other slightly basic anions. In particular, the hydration enthalpy of acetate is calculated using the Born-Haber approach, from lattice energies, heats of solution, and the hydration energies of several cations. The hydration enthalpy of acetate (-375 kJ/mol) is similar to that of chloride ({355 kJ/mol), nitrite ({383 kJ/mol), and nitrate ({370 kJ/mol), which are all considerably less exothermic than fluoride ({497 kJ/mol). This was somewhat unexpected, since hydration enthalpies generally correlate well with the acid-base properties of an ion, and acetate is more basic than fluoride. Factors influencing the solubility and acid-base properties of acetates, such as the electron donating and hydrophobic nature of the methyl group, are discussed in light of the thermodynamic data.
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