الفهرس | Only 14 pages are availabe for public view |
Abstract Random thermal motion of ions in solutions of strong electrolytes constantly brings anions and cations into proximity. Electrostatic attraction then alters the ionic motions so as to bring the ions closer together, occasionally to contact or near contact distances. Such pairs remain together until sufficiently large thermal fluctuations again send the ions apart. The tendency of the ions to associate in this way depends upon the balance between the interionic coulomb forces and thermal energy – thus upon the ion valancies, the dielectric constant and the temperature. It depends also on the solvation energy of the ions. Since the heat of solutions is small, dissolution of soluble salt as free ions requires sufficient solvation energy almost completely offset the lattice energy. Dissolution as ion-pairs requires solvation energy only approximately equivalent to the sublimation energy. Thus poor solvation promotes ion association. |