CHEM 1B Lecture Notes - Lecture 11: Lattice Energy, Enthalpy, Exothermic Process
Document Summary
Molecular view of dissolution: solvent-solvent, solute-solute, solvent-solute interactions. If solute-solvent interactions are strong, the dissolution is going to be energetically favored. The change in enthalpy ( h solution ) resulting from dissolving 1 mole of a substance in an excess amount of solvent. Endothermic ( h solution > 0) if | hlattice| > | hhydration| Exothermic ( < 0) if | hlattice| < | hhydration| Example of lattice energy: kf (s) k (g) + & f- (g) f- (aq) Hydration energy example: k+ (g) k+ (aq) & f- (g) f- (aq) Dissolution energy example: kf (s) k+ (aq) + f- (aq) Role of entropy: even if the dissolution is endothermic ( hsolution > 0) favor dissolution because of the gain in entropy- the degree of system disorder. Hsolution nacl = +3. 87 kj/mol (endothermic) but can be easily dissolved in water. Factors affecting solubility: a molecular structure of the solvent and solute.
