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Acta Phys. -Chim. Sin.  2009, Vol. 25 Issue (12): 2417-2421    DOI: 10.3866/PKU.WHXB20091120
Article     
Enthalpy of Formation, Heat Capacity and Entropy of Melamine
LIU Peng, XIONG Wei, HU Shan-Zhou, LI Xi, TAN Zhi-Cheng
Deparment of Chemistry, School of Sciences, Wuhan University of Technology, Wuhan 430070, P. R. China; Thermochemisty Laboratory and China Ionic Liquid Laoratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning Province, P. R. China
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Abstract  

The thermodynamic properties of melamine were studied by multiple thermochemical methods. A bomb combustion calorimeter was used to determine the combustion heat of melamine at 298.15 K. According to the results, we calculated the standard molar enthalpy of combustion and standard molar enthalpy of formation of melamine: △cHΘm=(-2455.17±4.65) kJ·mol-1; △fHΘm =(-763.38±5.16) kJ·mol-1. The bond enthalpy of C≈N (between single bond and double bond) in melamine was then estimated to be 458.30 kJ·mol -1 according to the ralationship between bond enthalpy and combustion enthalpy. This value is larger than that of C—N but smaller than that of C=N. Heat capacity measurements were carried out in a small sample adiabatic calorimeter from 80 to 385 K. We obtained △fHΘm at different temperatures between 80 and 385 K using the heat capacity data. Through calculation with the values of heat capacity, the relationship between the standard molar enthalpy of formation and temperature is also presented as a functional equation. We also measured the thermol stability of melamine by the thermogravimetry-differential scanning calorimetry (TG-DSC) technique, which showed a thermal decomposition peak at 603.37 K for the DSC curve.



Key wordsHeat capacity      Melamine      Combustion heat      Adiabatic calorimeter     
Received: 10 July 2009      Published: 28 September 2009
MSC2000:  O642  
Corresponding Authors: LIU Peng     E-mail: chemliup@whut.edu.cn
Cite this article:

LIU Peng, XIONG Wei, HU Shan-Zhou, LI Xi, TAN Zhi-Cheng. Enthalpy of Formation, Heat Capacity and Entropy of Melamine. Acta Phys. -Chim. Sin., 2009, 25(12): 2417-2421.

URL:

http://www.whxb.pku.edu.cn/10.3866/PKU.WHXB20091120     OR     http://www.whxb.pku.edu.cn/Y2009/V25/I12/2417

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