Studies on Volumetric and Viscometric Properties of Nitrobenzene and Alkanols Mixtures

Abstract

Densities and viscosities of binary mixtures of Ethanol + Nitrobenzene (NB), n-Propanol + Nitrobenzene (NB), /so-Propanol + Nitrobenzene(NB), n-Butanol + Nitrobenzene (NB), iso- Butanol + Nitrobenzene (NB), n-Amyl alcohol + Nitrobenzene (NB), iso-Amyl alcohol + Nitrobenzene (NB) and Propylene glycol + Nitrobenzene (NB) have been studied over the entire range of composition (0 < x2 < I) at 298.15- 323.15K with an interval of 5K. The density of alcohols in pure state was found to be in the order of Propylene glycol> n-Amyl alcohol > n-Butanol > n-Propanol > Ethanol and iso-Amyl alcohol> iso-Butanol > iso-Propanol The values of densities of Alkanols + NB at equi-mole fraction systems has been found to be in the order of Ethanol+NB> n-Propanol+NB > n-Butanol+NB > n-Amyl alcohol +NB> Propylene glycol NB and iso-Propanol+NB> iso-Butanol+NB> iso-Amyl alcohol+NB The value of density of Alkanols in NB decreases with the increasing of composition of the Alkanols. The decrease of density with composition of Alkanols can be attributed to solute-solvent interaction. The densities of all Alkanols in pure state increase with the increasing of carbon number which may depend on the molecular weight of alcohols, structural formula and H-bonding of alcohols. The densities decrease regularly with the increasing of temperature. This is due to the thermal agitation and hence the weaker the dipole-dipole interaction or dissociation of H-bonding are occurred. At the 0.5 mole fraction, the density of Ethanol+NB is higher than other higher chain or branched chain Alkanols indicating that the nature of association of NB mostly disrupted in higher or branched chain Alkanols. The excess molar volume, VE for all the systems are positive over the entire range of composition, showing maxima at 0.5-0.8 mole fraction of Alkanols. The values of maxima of VE of Alkanols in NB solutions was found to be in the order of Propylene glycol+NB > n-Amyl alcohol+NB > n-Butanol+NB > n-Propanol+NB > Ethanol+NB and iso-Amyl alcohol+NB > iso-Butanol+N13 > iso-Propanol+NB and iso-Amyl alcohol+NB > n-Amyl alcohol+NB and iso-Butanol+NB > n-Butanol+NB and iso-Propanol+NB > n-Propanol+NB The increasing of VE with carbon chain length of Alkanols may be related to increase of the size of Alkanols. The values of VE for the studied Alkanols increase with the increase of temperature. The observed values of VE for the mixtures have been explained in terms of physical, chemical and geometrical contributions. The viscosity coefficients, ƞ of Alkanols + NB mixtures at six different temperatures have also been determined. The viscosities decrease initially slowly up to ~0.5-0.8 mole fraction of Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, n-Amyl alcohol, iso-Amyl alcohol and Propylene glycol and later on, the viscosity increases sharply until the pure alcohol is reached. The viscosity of NB + Alkanols mixture at 0.5 mole fraction has been found to be in the order of Propylene glycol + NB> n-Amyl alcohol+ NB> n-Butanol >n-Propanol+ NB > Ethanol+ NB and iso-Amyl alcohol+ NB> iso-Butanol + NB > iso-Propanol+ NB and iso- Amy1 alcohol + NB > n- Amy1 alcohol + NB and iso-Butanol + NB> n-Butanol + NB and iso-Propanol + NB > n-Propanol + NB There is a marked decrease in the viscosity with increase of temperature for all the studied alcohols. This ascribed that the Alkanols + NB solutions are less stable at higher temperature. The increasing of viscosity with carbon number of Alkanols or branched chain Alkanols ascribed that the solution resistance increases with the increase of carbon chain length or branched chain. The linear dependence of lnƞ against 1/T shows for the all studied Alkanols + NB mixtures. The branched chain isomers are less stable than linear chain isomer at higher temperature. The excess viscosity, ƞ E values are found to be negative indicating that the Alkanols + NB system are non ideal. Excess viscosities are negative at all the temperatures over the entire range of composition for all the systems with minima occurring between 0.6-0.8 mole fractions. The negative excess viscosity, ƞ E of all the studied Alkanols + NB indicate that the dissociation of components through dispersive forces or steric hindrance. The position of minima virtually does not change remarkably with the variation of temperature. The values of the minima are in the order: Propylene glycol+NB> n-Amyl alcohol+NB > n-Butanol+NB > n-Propanol+NB > thanol+NB and iso-Amyl alcohol+NB> iso-Butanol+NB > iso-Propanol±NB and iso-Amyl alcohol+NB > n - Arnyl alcohol+NB and iso-Butanol±NB > n-Butanol+NB and iso-Propanol+NB > n-Propanol+NB The hydrophobic effect increases with the increasing of carbon chain length of alcohols. This indicates that the ƞ E decreases with the decrease of carbon number. The positive VE, negative ƞ E and negative interaction parameter (ɛ) for the studied Alkanols + NB systems indicate that dispersion force is dominant. Some disruptive force causing volume expansion may be present and it is more than compensated by volume contraction. The thermodynamic parameters such as free energy (∆G*), enthalpy (∆G*), and entropy (∆S*) change of activation for the viscous flow for these systems were examined for the entire range of composition. The free energy (∆G*) were found to be positive in magnitude indicating that the kinetic species involved in forming cavities or holes in the liquid medium is given by the work required in forming the hole against surface tension of the solution. The negative excess free energy, ∆G*E indicate that the strong dispersion force in Alkanols+ NB solution is dominant. The ∆H* values are positive for all the systems indicate that positive work has to be done to overcome the energy barrier for the flow process. The ∆S* values are found to be very small for all the studied systems indicating that the effects of ∆S* are negligible. The excess properties (VE, ƞ E, ∆G*E) data have been fitted by the least square method to the four parameters Redlich-Kister equation and the values of the parameter ai and standard deviation have been reported. The volumetric properties are fully consistent with viscometric and thermodynamic properties.