CHEM 123N Lecture Notes - Lecture 7: Solution Process, Intermolecular Force, Lattice Energy
12 Nov 2018
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I(cid:296)dividual substa(cid:296)ce"s che(cid:295)ical (cid:296)ature u(cid:296)cha(cid:296)ged, (cid:296)o reactio(cid:296) occurs. Particles do(cid:296)"t separate o(cid:296) sta(cid:296)di(cid:296)g, are suspe(cid:296)ded. Solutions are composed of two components - the solvent [major component] and the solute [minor component]. Except for gas-gas solutions, intermolecular forces are necessary to understand why certain substances dissolve in others. Solutions will form when solv/solv, sol/solv and sol/sol forces are si(cid:295)ilar. (cid:718)like dissolves like. (cid:719) Ionic dissolves in polar, nonpolar solids dissolve in nonpolar solvents, etc. Dissolution of solute in solvent has associated free energy change. Enthalpy is a measure of energy change. Delta g being negative means the solute dissolves spontaneously. Delta g being positive means that the solute requires energy to dissolve. Delta h - enthalpy of solution or heat of solution. Molecular randomness usually increases, delta s solution is usually positive. Negative delta h is exothermic, positive delta h is endothermic. Delta h solution is an interplay of solute and solvent interactions.
