Studies on the Thermodynamics of Association of Ions in Aqueous Solutions

Nair, V. S. Krishnan (1958) Studies on the Thermodynamics of Association of Ions in Aqueous Solutions. PhD thesis, University of Glasgow.

Abstract

The thermodynamics of ion association in aqueous solutions of 1:1 and 2:2 valency type electrolytes have been studied. The thesis is divided into three parts together with an appendix. In part I, the uncharged ion pairs formed by the thallous ion with the aside, nitrate and bromide ions have been studied by solubility measurements on thallous iodate in sodium azide and potassium nitrate solutions at 0, 10, 25 and 40°C. , and on thallous bromide in sodium perchlorate and potassium nitrate solutions at 25 and 40°C. Conductivity measurements of thallous chloride solutions at 40°C and on saturated solutions of thallous bromide at 25 and 40°C have also been made. The heat and entropy of association are compared with data for other uncharged ion pairs. Part II deals with a study of association of bivalent cations with the sulphate ion using the cell H2, Pt HCl I, MSO4 AgCl, Ag in which e. auf. s were measured to an accuracy of +/-0.01 m.v. A detailed investigation of the second dissociation of sulphuric acid, has been made over the temperature range 0°C to 45°C using the cell, H2, Pt | HCl, H2SO4 I AgCl, Ag and the results obtained are discussed and compared the with the available data in literature. The heat of dissociation of bisulphate is in good agreement with values obtained by calorimetric and spectraphotometric methods. The ionic association in solutions of the sulphates of magnesium, zinc, cobalt, nickel and manganese has been studied at various temperatures in the range 0°C to 45°C. , in a range of ionic strength and the thermodynamic functions have been derived. Part III consists of a general discussion of the results. The entropies of the various ion pairs have been estimated, taking into account both translational and rotational terms. The heat and entropy data have been discussed in relation to the factors involved in the association process. A S hydration of the ion-pairs are compared in relation to their size, and a good linear relationship between A S hyd (ion pair) and reciprocal of interionic distance has been observed for the 1:1 ion pairs (including some silver salts). A similar relationship is indicated for the sulphates of the transition metals cobalt, nickel and manganese. An appendix is included dealing with a spectro- photometric study of the equilibrium HCrO4- ↔ H+ +CrO4-- at 25°C, at wavelengths 355, 365, 370, 375 and 385 m.u. A value of 2.97x10e-7 obtained for the dissociation constant is in agreement with the potentiometric value.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Physical chemistry, Thermodynamics
• Date of Award: 1958
• Depositing User: Enlighten Team
• Unique ID: glathesis:1958-79266
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 31 Mar 2020 09:09
• Last Modified: 31 Mar 2020 09:09
• URI: https://theses.gla.ac.uk/id/eprint/79266