Open AccessNEAR HYDRATION OF SINGLY CHARGED MONOATOMIC IONS IN EXTREMELY DILUTED SOLUTIONS: THE EFFECT OF TEMPERATURE AND PRESSURE
Author(s) -
Віктор Іванович Булавін,
Іван Миколайович В’юник,
Андрій Вікторович Крамаренко,
Олександр Іванович Русінов
Publication year - 2021
Publication title -
vestnik nacionalʹnogo tehničeskogo universiteta "hpi". himiâ, himičeskaâ tehnologiâ i èkologiâ/vìsnik nacìonalʹnogo tehnìčnogo unìversitetu "hpì". serìâ: himiâ, himični tehnologiï ta ekologiâ
Language(s) - English
Resource type - Journals
eISSN - 2708-5252
pISSN - 2079-0821
DOI - 10.20998/2079-0821.2021.01.04
Subject(s) - ion , chemistry , solvation , diffusion , ionic radius , analytical chemistry (journal) , molality , conductivity , solvation shell , thermodynamics , aqueous solution , physics , organic chemistry , chromatography
The diffusion coefficient and the distance of translational displacement of Li+, Na+ K+, Cs+, Cl– and Br– ions in water at 298.15 K – 423.15 K (25 K step) and pressure from 0.0981 to 784.5 MPa (98.1 MPa step) were calculated from the literature data on limiting molar electrical conductivity. The values for these ions increase with pressure growth from 0.0981 to 98.1 MPa at 298.15 K. Further pressure increase (up to 785 MPa) leads to decrease in . Temperature growth under isobaric conditions leads to an increase in . Parameter (– ri) (deviation from the Stokes–Einstein law, ri is ion structural radius) was used as a criterion for the type of ion solvation. It is shown that Li+ and Na+ ions behave as cosmotropes, or positively solvated structure–forming ions having (– ri) > 0. The Cs+, Cl–, Br– ions behave as chaotropes, or negatively solvated structure–breaking ions having (– ri) < 0. For the K+ ion, the (– ri) deviation is alternating. At 0.0981 MPa and 298.15 K, the K+ ion is a chaotrope. But at 320 K (Tlim) parameter (– ri) = 0. It corresponds to the transition from negative to positive solvation. Above Tlim at P = const, the K+ ion is a cosmotrope. At 298.15 K and up to 98.1 MPa, the pressure causes the same change in the (– ri) deviation as the temperature. On the contrary, at 320 K and higher, the pressure affects the near hydration in the direction opposite to the temperature.