Thermodynamics of acrylic acid from T=5 K to T=330 K

The temperature dependence of the standard molar heat capacity C-p,m(O), of a sample of acrylic acid (total mole fraction of impurities, x = 0.0011)ha s been studied in an adiabatic vacuum calorimeter at temperatures between T = 5 K and T = 330 K to within 0.2 per cent at T > 40 K. The temperature an d enthalpy of melting of the compound have been measured. The data obtained were used to determine the temperature, enthalpy, and entropy of melting o f pure acrylic acid and to calculate its thermodynamic functions C-p,m(O)(T ), Delta(0)(T)H(m)(O), Delta(0)(T) S-m(O), and Phi(m)(O) in the range T --> 0 to T = 330 K. From literature data on the standard enthalpy of formation and the absolute entropy estimated in the present work, the standard molar entropy of formation Delta(f)S(m)(O), and the standard molar Gibbs free en ergy of formation Delta(f)G(m)(O) and logarithm of the thermodynamic consta nt of the formation reaction Ig Kf of acrylic acid from the corresponding e lements in their standard states at T = 298.15 K have been calculated. (C) 1999 Academic Press.