Volumetric And Viscometric Investigation Of Aqueous Solution Of [C_nmim][bF4](n=3,4)

Ionic liquids(ILs)have attracted much attention for their unique properties.Learning the properties of ionic liquids is the basic for the usage of ILs.It usually is made into solution for the relatively high viscosity.Some studies have proved that the dilute aqueous solution of imidazole tetrafluoroborate ionic liquids have excellent effect in the practical applications.Hence,the aqueous solution of imidazole tetrafluoroborate ionic liquids{[Cnmim][BF4](n = 3,4)} were selected as the research objects in this paper and the physicochemical properties of this binary mixture were discussed.Density and viscosity of aqueous[C,mim][BF4](n = 3,4)were measured at the temperature range from 288.15 to 318.15 K with a step of 5 K under atmospheric pressure.Moreover,in order to ensure the experiment condition is dilute solution,all the concentrations of the aqueous solutions were controlled bellow 1.000 mol-kg-1.Firstly,the values of apparent molar volumes for aqueous[Cnmim][BF4](n = 3,4)were obtained.According to Redlich-Mayer equation,the empirical parameters(5v and Bv)and the limiting apparent molar volume at infinite dilution,?Vi0,were acquired and obtained the nature of ion-ion and ion-solvent interactions in the aqueous solution.Based on the equation of ?Vi0 and T,the limiting apparent molar expansibilities,E??,and Hepler's paremeter were calculated.The results manifested that[Cnmim][BF4](n = 3,4)act as structure breaker in water over the temperature ranges.Secondly,through the Jones-Dole empirical equation,the viscosity coefficient A and B of aqueous[Cnmim][BF4](n = 3,4)were obtained.In addition,the standard molar activation Gibbs free energy of solute,??2?0,were obtained according to the Eyring transition state theory,and the activation entropy,?S2?0.as well as activation enthalpy,?H2?0,can be calculated by fitting ??2?0 against T.Using a semi-empirical method the viscosity of aqueous[Cnmim][BF4](n = 3,4)were predicted and the result showed a good agreement with experimental values.Finally,the volume properties at infinite dilution were also investigated using Pitzer's equation the result showed that the limiting apparent molar volume at infinite dilution of Redlich-Mayer's and Pitzer's equation were mutually proved.