Browsing by Author "Das, Asim K."

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    Free Energies and Entropies of Transfer of Hydrogen Halides from Water to Aqueous Alcohols and the Structure of Aquo-organic Solvents
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (05), 1978) Bose, Kumardev; Das, Kaushik; Das, Asim K.; Kundu, Kiron K.
    Free energies ΔG0t and entropies ΔS0t of transfer of HCl from water to ethanol + water and propan-2-ol + water mixtures have been determined from the standard potentials E0 of the cell Pt, H2(g, 1 atm)|HCl (m), solvent|AgCl–Ag. ΔG0t values for hydrogen and halide ions have been obtained by a simultaneous extrapolation procedure applied to ΔG0t(HCl), ΔG0t(HBr) and ΔG0t(HI), values of the last two being taken from previous papers. The chemical parts of the ionic ΔG0t values in these and two other aquo-alcoholic systems have been interpreted in terms of ion-solvent interactions of the acid–base type modified by solvent structural effects. Characteristic humps observed in ΔS0t(HX)-composition profiles for aqueous ethanol, propan-2-ol and t-butanol mixtures have been shown, by means of a semi-quantitative theory, to result from a well-known feature common to these solvents, viz., promotion of water structure in highly aqueous compositions. This theory has then been used to obtain information regarding solvent structure in other aquo-organic solvent systems and to stress the usefulness of ΔS0t as a probe for solvent structuredness.
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    Standard Potentials of M/M+ (M=Li, Na, K, Rb or Cs) Electrodes in Dimethyl Sulphoxide+Water Mixtures at 25°C and Related Ion-Solvent Interactions in the Solvents
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (08), 1974) Das, Asim K.; Kundu, Kiron K.
    The standard electrode potentials GE’) of M/M+ (M = Li, Na, K, Rb and Cs) electrodes in aqueous solutions of dimethyl sulphoxide (DMSO) (containing 10, 20, 40 and 60 wt. % DMSO) have been determined at 25°C from e.m.f. measurements of cells of the type: M(Hg)|MCl(/n), solvent] AgCl-Ag, obtaining the activity of metals in amalgams with the help of a similar type of cell in water. The free energies of transfer of MCI, AGt°(MCl) (mole fraction scale) from water to each of these solvents computed from these values and those of sEXg-AgCi obtainable from the literature, rise sharply from Li+ to Na+, and fall from Rb+ to Cs+ with a maximum between Na+ and Rb+. This is considered as due to the superimposition of “ soft-soft ” interactions on the “ electrostatic inter actions ” between the ions and the negative charge centres of hydrogen-bonded solvent complexes. The AG? (I) values for individual ions, obtained by a method of “ simultaneous extrapolation ” arc shown to be largely determined by the “ acid-base ” type ion-solvent interactions as observed in methanol+water mixtures.