Browsing by Author "Khoo, Kean H."

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    Activity Coefficients for the System HCI+COCI2+H2O at 298.15 K Effects of Higher-order Electrostatic Terms
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (08), 1978) Khoo, Kean H.; Lim, Tiong-Koon; Chan, Chee-Yan
    Activity coefficients for HCl in the system HCl + CoCl2 H2O, at 298.15 K and at constant total ionic strengths of 0.1, 0.5, 1.0, 2.0 and 3.0 mol kg–1, have been measured by an e.m.f. method. The results have been treated using Scatchard's and Pitzer's equations for mixed electrolyte solutions and activity coefficients for the salt have been derived. Although Scatchard's treatment generally gave a more accurate fit to the experimental data, the fit to Pitzer's equation, though satisfactory, could be significantly improved for the six HCl + NCl2 systems considered, provided that recognition is given to the contribution of higher-order electrostatic terms beyond the Debye–Huckel approximation to the thermodynamic properties of asymmetrical mixtures.
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    Activity Coefficients for the System HCl+BaCl2+H2O at 298.15 K: Comparison of Scatchard’s and Pitzer’s Interpretations
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (04), 1978) Khoo, Kean H.; Chan, Chee-Yan; Lim, Tiong-Koon
    Activity coefficients of hydrochloric acid in aqueous solutions of barium chloride have been measured at 298.15 K at constant total ionic strengths of 0.1, 0.5, 1.0, 2.0 and 3.0 mol kg-1 using hydrogen-silver-silver chloride cells. The data were interpreted in terms of Scatchard’s and Pitzer’s equations whereupon it was found that, whereas the former gave a more accurate fit of the experimental results, the latter were nevertheless quite adequate and more convenient. Contrary to Harned and Gary’s conclusions, hydrochloric acid follows Hamed’s rule equally well at all these ionic strengths, while quadratic terms arc clearly warranted for barium chloride at Z = 2.0 and 3.0 mol kg-1.
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    Activity Coefficients of Hydrochloric Acid in Mixtures with Potassium Chloride in Methanol+Water Solvents from Electro motive Force Measurements at 298.15 K
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Chee-Yan, Chan; Khoo, Kean H.
    E.m.f. measurements of the cell, PtlHjlHCKw,), KC1(w2), methanol(Y), water,AgCl|Ag, have been made at 298.15 K for solvent compositions X = 0, 10, 30, 40 and 45 % (w/w) of methanol, the total ionic strength of each solution being 1 mol kg-1. The logarithm of the mean ionic molal activity coefficient of hydrochloric acid was found to vary linearly with potassium chloride molality for the systems in which the solvent mixture contained 0, 10 and 30 % methanol. For methanol composition above 30 %, the activity coefficient of the acid was a quadratic function of the salt concentration. Secondary medium effects are discussed in relation to differences in specific ionic interactions for the different electrolyte mixtures in water and in the mixed solvents.