Ionic association and thermodynamic functions for solvation interaction of nano copper sulfate (NCS) with methyl red (MR) in mixed methanol (MeOH) –Water solvents
Assiut University Journal of Multidisciplinary Scientific Research
Specific conductivities for nano copper sulfate (NCS) have been measured in binary mixed solvent-solvent with methyl alcohol (MeOH) mass fraction 0%, 20% and 40% (W/W) (MeOH-H 2 O) at different temperatures: 298.15, 303.15 ,308.15 and 313.15 K (with a step of 5 K) and in the presence of methyl red indicator (MR) as chelating agent. The experimental data have been analyzed by the use of Fuoss-Shedlovsky conductivity model (FSH) equation. Molar conductance (Λ m ), limiting molar conductance (Λ 0
... , Walden product (Λ 0 η 0 ), ion-pair association constant (K A ) and the standard thermodynamic parameters for the association (ΔG°A, ΔH°A and ΔS°A) were estimated and discussed in absence and in presence of methyl red (MR). All the thermodynamic parameters were evaluated for the interaction of nano copper sulfate (NCS) with methyl red (MR).The ion pair association constant (K A ) and the different thermodynamic functions were increased by increasing the percentage of methanol by molar mass and increase of temperature favoring more ion -solvent interactions between nano copper sulfate (NCS) and methyl red (MR). The effect of formation of hydrogen bond (FHB) in solution also has been studied. The obtained results show that the association constant (K A ) was increased as the relative bulk permittivity of the solvent decreased while the molar conductance (Λ m ) and the limiting molar conductivities (Λ 0 ) were decreased. Furthermore, as the temperature increased, the association constant (K A ) values were increased indicating the association process is endothermic.