Dissolution, of ionic crystals

Water is the most common solvent used to dissolve ionic compounds. Principally, the reasons for dissolution of ionic crystals in water are two. Not stated in any order of sequence of importance, the first one maybe mentioned as the weakening of the electrostatic forces of attraction in an ionic crystal known, and the effect may be alternatively be expressed as the consequence of the presence of highly polar water molecules. The high dielectric constant of water implies that the attractive forces between the cations and anions in an ionic salt come down by a factor of 80 when water happens to be the leaching medium. The second responsible factor is the tendency of the ionic crystals to hydrate. 

Corrosion refers to the loss or conversion into another insoluble compound of the surface layers of a solid in contact with a fluid. The solid is normally a metal, but the term corrosion is also used to refer to the dissolution of ionic crystals or semiconductors. In the majority of cases the fluid is water, but an important exception is the reaction of metallic surfaces with air at high temperature, leading to oxide formation, or, in industrial environments, to sulphides, etc. In the context of this book, corrosion of metals or semiconductors in contact with aqueous solution or humid air at normal temperatures is of predominant interest. 

Dissolution of Ionic Crystals in Acidic and Alkaline Media (5). All ionic crystals are not soluble and many insoluble substances are etched In acidic and alkaline media. The ideas of dissolution in terms of double layer potentials can be extended to such situations in which it is considered that protons or hydroxyl ions of an acid or an alkali are complexingagents for anions or cations, respectively. For example, in the dissolution of MgO in aqueous HCI, H+ ions are the complexing agents for 0 such that OH and HjO are produced. 

Similar observations hold for solubility. Predominandy ionic halides tend to dissolve in polar, coordinating solvents of high dielectric constant, the precise solubility being dictated by the balance between lattice energies and solvation energies of the ions, on the one hand, and on entropy changes involved in dissolution of the crystal lattice, solvation of the ions and modification of the solvent structure, on the other [AG(cryst->-saturated soln) = 0 = A/7 -TA5]. For a given cation (e.g. K, Ca +) solubility in water typically follows the sequence... 

Molecular Aspects on the Dissolution and Nucleation of Ionic Crystals in Water... 

MOLECULAR ASPECTS ON THE DISSOLUTION AND NUCLEATION OF IONIC CRYSTALS IN WATER... 

The logarithmic dependence of the dissolution rate on the electrode potential can be explained in the case of ionic crystals under the following assumptions (a) The dissolution process is far from equilibrium, (b) The passage of cations and anions can be treated as independent electrochemical reactions. The rate of each of them depends logarithmically on the electrode potential and on the chemical potential of the species in question in the solid phase, (c) According to the... 

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