Advertisement

Relation between the Kinetics and Thermodynamics in the Endothermic Decomposition of Solids

  • Z. Jerman
Chapter

Abstract

Decomposition measurements with Mg(OH)2 in water vapour, performed by a technique based on recording the temperature inside the specimen, on its surface and in the furnace metal block, were evaluated by calculating the heat-flow into the specimen, maximum reaction rate and first-order rate constants« The temperature dependence of the latter was correlated using the Planck radiation law and respecting the influence of the equilibrium proximity. The results were: A=6.6×-1, E=135.7 kJ/mole. Since E=ΔH+ RT, the activation enthalpy ΔH≠ = 130.3 kJ/mole at 650 K is greater than the enthalpy change from tabulated data (math)(kJ/mole) by 12 kJ/mole. It corresponds to the enthalpy difference between a low-temperature (active) and high-temperature (stabile) MgO from Mg(0H)2. Therefore, the activation enthalpy here is equivalent to the enthalpy change of the reaction Mg(OH)2(s)sMgO(active)+H2O(g). This type of mechanism may be common for the endothermic decomposition of solids.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. (1).
    M. Polanyi and E. Wigner, Z.Phys.Chen.139A (1928) 439Google Scholar
  2. (2).
    Z. Jerman, Collection Czechoslov.Chem. Commun 38 (1973) 3210CrossRefGoogle Scholar
  3. (3).
    R.D. Shannon, Trans.Faraday Soc.60 (1964) 1902CrossRefGoogle Scholar
  4. (4).
    H.F. Cordes, J.Phys.Chem.72 (1968) 2185CrossRefGoogle Scholar
  5. (5).
    O.C. Niepce and G. Watelle, J.Chem.Soc.74 (1978) 1530Google Scholar
  6. (6).
    Z. German, Proceedings: Zborník VIII. celoštátnej kon-ferencie o termickej analýze, Vysoké Tatry 1979, p.79Google Scholar
  7. (7).
    R. Fricke and J. Lücke, Ztschr.Elektrochem. 41 (1935) 174Google Scholar

Copyright information

© Springer Basel AG 1980

Authors and Affiliations

  • Z. Jerman
    • 1
  1. 1.Chemopetrol, Výzkumný ústav anorganické chemieÚstí nad LabemCzechoslovakia

Personalised recommendations