The low-temperature heat capacity Cp.m of 2-methyl-2-butanol was precisely measured in the temperature range from 80 to 305 K by means of a small sample automated adiabatic calorimeter.Three solid-solid phase transitions and one solid-liquid phase transition were found at T=146.355,149.929,214.395 and 262.706 K from the experimental Cp-T curve,respectively.The dependence of heat capacity on temperature was fitted to the following polynomial equations with a least square method.In the temperature range of 80 to 140 K,Cp.m=39.208+8.0724X-1.9583X2+10.06X3+1.799X4-7.2778X5+1.4919X6,X=(T-110)/30;in the temperature range of 155 to 210 K,Cp,m=70.701+10.631X+12.767X2+O.3583X3-22.272X4-O.417X5+12.055X6,X=(T-182.5)/27.5;in the temperature range of 220 to 250 K,Cp.m=99.176+7.7199X-26.138X2+28.949X3+O.7599X4-25.823X5+21.131X6,X=(T-235)/15;and in the temperature range of 270 to 305 K,Cp.m=121.73+16.53X-1.O732X2-34.937X3-19.865X4+24.324X5+ 18.544X6,X=(T-287.5)/17.5.The molar enthalpies of these transitions were determined to be 0.9392,1.541,0.6646 and 2.239 kJ·mol-1,respectively.The molar entropies of these transitions were determined to be 6.417,10.28,3.100 and 8.527 J·K-1·mol-1,respectively.The thermodynamic functions [HT-H298.15]and [ST-S298.15],were derived from the heat capacity data in the temperature range of 80 to 305 K with an interval of 5 K.
展开▼
