Thermodynamic Properties of Sodium Methanesulfonate

The isobaric heat capacity {C₏, ₌} of crystalline sodium methanesulfonate NaCH3SO3 was determined by low-temperature adiabatic vacuum calorimetry in the temperature range from 7. 45 to 348. 42 K. The heat capacity curve did not demonstrate any phase transitions or thermal anomalies. The experimental heat capacities were approximated by a linear combination of the Einstein–Planck functions, whose extrapolation to 0 K was performed using the Debye cube law. The absolute entropy S₌^^ (T), enthalpy H₌^^ (T) - H₌^^ (0), and temperature contributions to the Gibbs energy G₌^^ (T) - ~H₌^^ (0) were calculated from the heat capacity data by analytical integration of the corresponding functions. The standard enthalpy of solution of NaCH3SO3 in water at 298. 15 K { {ₒ₎₋}}H₌^^ was determined by solution calorimetry. The standard thermodynamic functions of formation of NaCH3SO3 in the crystalline state at 298. 15 K—the enthalpy { ₅}H₌^^ and the Gibbs energy of formation { ₅}G₌^^ —were calculated from the experimental data. The increment of the methanesulfonate ion to the main thermodynamic functions was estimated.