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

• ΔsolHmθ for [C4mim][OAc] were obtained in the temperature range of (288.15–308.15 ± 0.01) K.
• The ΔCp,mθ, ΔCpθ, (ΔH+ + ΔH−) and ΦL for [C4mim][OAc] were also calculated.
• The values of Pitzer's parameters linearly increase while temperature elevates.

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 5 K. 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−) = –531.6 kJ mol−1, at 298.15 K. 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 = 339 J K−1 mol−1 was obtained from the slope of the regression line, and the specific heat capacity of solution, ΔCpθ = 1.70 J g−1 K−1, was also determined for [C4mim][OAc].