Thermodynamics Research Center / ThermoML | Thermochimica Acta

Low temperature heat capacity of .alpha.-Na2NpO4

Smith, A. L., Griveau, J.-C., Colineau, E., Raison, P. E., Konings, R. J. M.
Thermochim. Acta 2015, 617, 129-135
ABSTRACT
The heat capacity of .alpha.-Na2NpO4 has been measured for the first time in the temperature range 2.1-301 K using a Quantum Design PPMS (Physical Property Measurement System) calorimeter. The heat capacity and entropy values at 298.15 K have been derived as Cop,m(.alpha.-Na2NpO4, cr, 298.15 K) = (151.9 +- 4.6) J K-1mol-1and Som(.alpha.-Na2NpO4, cr, 298.15 K) = (178.3 +- 4.3) J K-1mol-1, respectively. The standard entropy of .alpha.-Na2NpO4 follows the trend shown by the isostructural compound .alpha.-Na2UO4 and the alkaline earth uranates MgUO4, SrUO4, BaUO4, and Cs2UO4. When combined with the entropies of the constituent elements, these data yield a standard entropy of formation at 298.15 K as DSom(.alpha.-Na2NpO4, cr, 298.15 K) = - (385.1 +- 4.3) J K-1mol-1. Using the enthalpy of formation tabulated in the literature, the standard Gibbs energy of formation was calculated at 298.15 K as DGom(.alpha.-Na2NpO4,cr, 298.15 K) =(-1649.0 +- 5.8) kJ mol-1.
Compounds
# Formula Name
1 Na2NpO4 sodium neptunate
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Gas
  • relaxation calorimetry
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Gas
  • relaxation calorimetry
  • 1
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • RELAXCAL
  • 210
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 2
  • Temperature, K; Crystal 2
  • Pressure, kPa; Crystal 2
  • Crystal 2
  • RELAXCAL
  • 113
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 2
  • Temperature, K; Crystal 2
  • Pressure, kPa; Crystal 2
  • Crystal 2
  • RELAXCAL
  • 14
  • POMD
  • 1
  • Molar entropy, J/K/mol ; Crystal 2
  • Temperature, K; Crystal 2
  • Pressure, kPa; Crystal 2
  • Crystal 2
  • relaxation calorimetry
  • 14
  • POMD
  • 1
  • Molar enthalpy, kJ/mol ; Crystal 2
  • Temperature, K; Crystal 2
  • Pressure, kPa; Crystal 2
  • Crystal 2
  • relaxation calorimetry
  • 14
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • RELAXCAL
  • 48
  • POMD
  • 1
  • Molar entropy, J/K/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • relaxation calorimetry
  • 48
  • POMD
  • 1
  • Molar enthalpy, kJ/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • relaxation calorimetry
  • 48