3 Part One. The Predicate

Ionic Theories
About the mid-1880’s, Arrhenius postulated in his ionization theory that (1) electrolytes are completely dissociated into their constituent ions in the limit of infinite dilution, (2) the equivalent conductance of the free ions is independent of concentration, (3) the equilibrium between the ions and the undissociatcd molecules conforms to the law of mass action. Thus, in the second postulate Arrhenius assumed that the decrease in conductivity with increasing concentration is due to the association of free ions to form neutral molecules. We now know that the original postulate is invalid since the mobility of the free ions decrease with increasing concentration owing to interaction between ions of opposite charge. In 1920, Bronstcd’s theory of specific ion interaction was based on the approximation that chemical interaction is limited to that between ions of opposite sign. By the reasoning given, it was shown that ions of the opposite chaigc are more likely to approach close to one another than are ions of the like charge, and this basic concept led to the considerable advances made by Brdnstcd in his own studies o f mixed electrolyte solutions.

The first statistical theory o f electrolytc solutions, the intcrionic attraction theory, was developed by Dcbyc and Huckcl in 1923 and its application has been remarkably successful in interpreting the behaviour of very dilute solutions. The ions are regarded as unpolarizablc point chaigcs distributed in a continuum possessing a dielectric constant identical with that of the pure solvent, and it is also recognized that ions group themselves a little eloser around an ion of the opposite chargc than they do around ions of the like chargc. This leads to an ion atmosphere surrounding each ion in solution. From the theory, it is sought to calculate the average potential energy of a given ion in solution due to all the other ions, assuming the medium to have the dielectric constant of the pure solvent. In the argument strong electrolytes are assumed to be completelydissociated into ions, and observed deviations from this ideal behavior are then ascribed to electrical interactions between the ions.

Mashq 3. Matnning asosiy tarkibini bir nechta jumlalar bilan bog'lang.

Mashq 4. Matndagi qaysi so'zlar "ommaviy harakatlar qonuni" ni anglatadi?

Mashq 5. Matnda quyidagi savollarga javob toping:

1. Ionlashuv nazariyasining asosiy qoidalari nimalardan iborat? 2. Arreniusning fikriga ko'ra, o'tkazuvchanlikning pasayishi kontsentratsiyaning oshishi bilan nima izohladi? 3. Brensted nazariyasi uchun qanday taxmin asos bo'ldi? 4. Eritilgan eritmalarning xatti-harakatlarini qaysi nazariya muvaffaqiyatli izohladi? 5. Debay va Xyukell nazariyasiga asoslangan eritmada ionlarning harakati qanday?

Mashq 6. Quyidagi jumlalarni to'ldiring:

1. The original postulate suggested by Arrhenius is invalid because...2. Bronstcd made considerable advances in... 3. The first statistical theory of cicctrolytc solutions was... 4. According to the theory developed by Debye and Hiickcl, an ion atmosphere surrounding each ion in solution is due to... 5. Using the theory by Debye and Hiickel one can calculate...