Viscometric and Thermodynamics Study of uni-bivalent Mixed Electrolytes in Aqueous Solutions at 293.15, 303.15 and 313.15K

Abstract

Viscosities (η) and apparent molar volumes (V_f) of the solutions of uni-bivalent mixed electrolytes in aqueous solutions have been determined at 293.15, 303.15and 313.15K. It is seen that the plots of ή_rel-1/√y verses √y   are linear, from which the values of coefficients A and B have been obtained by the method of least squares. The values of coefficient A are positive for the mixed electrolytes (NH₄)₂C₂O₄ + K₂C₂O₄, Na₂SO₄ + K₂SO₄ and (NH₄)₂SO₄ + K₂SO₄. The negative values of B in the case of Na₂SO₄ + K₂SO₄ and (NH₄)₂ SO₄ + K₂SO₄ show the presence of strong ion-ion interactions in the aqueous solution of these mixed electrolytes. In each case the values of A tend to decrease with the rise of temperatures which suggests further weakening of ion-ion interactions at elevated temperatures. The values of B are positive which tend to increase more positive with the rise of temperature there by suggesting the presence of strong ion-solvent interactions, which becomes stronger at elevated temperatures. The variation of  with. y, fraction of ionic strength due to the first electrolyte in the mixture of two electrolytes at different temperatures is linear. From   ή and V_Φ   data the values of coefficients A and B of Jones -Dole equation and that of V_^ and S_v  of Masson's equation have been  obtained. Besides the activation thermodynamic quantities Δμ₂^0#  , ΔH₂^0#and ΔS₂^0#  of viscous flow have also been calculated for the mixed electrolytes  in aqueous solutions. It is seen that the values of Δμ₂^0# are much larger as compared to those of Δμ₁^0# for all the uni-bivalent mixed electrolytes.  The values of TΔS₂^0# are negative while those of  ΔH₂^0#  are positive and that ΔH₂^0#  > TΔS₂^0#_, thereby suggesting that ion-solvent interaction for the mixed electrolyte system, are nearly complete in the ground state. Further these are the values of TΔS₂^0# and ΔH₂^0# indicate the transition state is associated with the bond breaking and increase in order.