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  • 1 Chinese Academy of Sciences Thermochemistry Laboratory, Dalian Institute of Chemical Physics Dalian P. R. China 116023
  • 2 Dalian Jiaotong University College of Environmental Science and Engineering Dalian China 116028
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Abstract  

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, CP,m (J K–1 mol–1)= 195.55+47.230 X–3.1533 X2+4.0733 X3+3.9126 X4 [X=(T–125.5)/45.5] for the solid phase (80~171 K), and CP,m (J K–1 mol–1)= 378.62+43.929 X+16.456 X2–4.6684 X3–5.5876 X4 [X=(T–285.5)/104.5] for the liquid phase (181~390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass translation of BMIBF4 was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BMIBF4 was determined to be ΔcHmo= – 5335±17 kJ mol–1. The standard molar enthalpy of formation of BMIBF4 was evaluated to be ΔfHmo= –1221.8±4.0 kJ mol–1 at T=298.150±0.001 K.

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