The Entropy of Formic Acid. The Heat Capacity from 15 to 300°K. Heats of Fusion and Vaporization
- 1 February 1941
- journal article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 9 (2) , 163-168
- https://doi.org/10.1063/1.1750869
Abstract
The heat capacity of solid and liquid formic acid has been measured from 15 to 300°K. The melting point is 281.40°K (0°C=273.10°K). The heat of fusion is 3031 cal. mole‐1 and the heat of vaporization at 298.10°K is 4754 cal. mole‐1. (1 mole=46.0260 grams.) The vapor pressure at 298.10°K is 4.31 cm of mercury. From the third law of thermodynamics and the calorimetric data the entropy has been calculated. To the value obtained from the calorimetric measurements an entropy of R/2 ln 2, due to the random orientation of hydrogen bonds in the solid which has been predicted by Pauling, has been added. This gives 31.51 cal. deg.‐1 mole‐1 for the entropy of the liquid at 298.10°K and 47.46 for the entropy of 46.0260 grams of gas, P=4.31 cm, in equilibrium with the liquid at 298.10°K. These are the values that should be used in thermodynamic calculations.Keywords
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