Читать книгу Geochemistry - William M. White - Страница 67
Example 2.5 Enthalpies (or heats) of reaction and Hess's law
ОглавлениеWhat is the energy consumed or evolved in the hydration of corundum (Al2O3) to form gibbsite (Al(OH)3)? The reaction is:
Answer: We use Hess's law. To use Hess's law, we need the standard state enthalpies for water, corundum, and gibbsite. These are: Al2O3: −1675.70 kJ/mol, H2O: −285.83 and Al(OH)3: −1293.13. The enthalpy of reaction is .
This is the enthalpy of reaction at 1 bar and 298 K. Suppose you were interested in this reaction under metamorphic conditions such as 300°C and 50 MPa. How would you calculate the enthalpy of reaction then?
