Study on the thermodynamic properties for ionic liquid [C4mim][OAc](1-butyl-3-methylimidazolium acetate)

Abstract

Using the solution-reaction isoperibol calorimeter, molar enthalpies of solution in water, ΔsolHm, for ionic liquid [C4mim][OAc] with different molalities were measured in the temperature range of (288.15–308.15±0.01)K with an interval of 5K. According to Archer's method or Pitzer's electrolyte solution theory, the values of the standard molar enthalpies of solution, ΔsolHmθ, the apparent relative molar enthalpy ΦL, and the parameters βMX(0)L, βMX(1)L were determined for [C4mim][OAc]. According to Krossing's theory of lattice energy, the hydration enthalpy of cation and anion in infinite dilution aqueous [C4mim][OAc] were calculated, (ΔH++ΔH−)=–531.6kJmol−1, at 298.15K. A linear relationship was found by plotting the experimental values of ΔsolHmθ against (T – 298.15)K. The standard molar heat capacity of solution, ΔCp,mθ=339JK−1mol−1 was obtained from the slope of the regression line, and the specific heat capacity of solution, ΔCpθ=1.70Jg−1K−1, was also determined for [C4mim][OAc].