Heat of Formation and High-temperature Heat Content of Manganous Oxide and Manganous Sulfate. High-temperature Heat Content of Manganese¹

Gibbs Energy of Formation of MnO: Measurement and Assessment

“…Southard and Shomate [16] reported high-temperature heat content (H o T À H o 298:15 ) of MnO in the temperature range from 519 to 1773 K by drop calorimetry. Samples of MnO were dropped from a platinum-rhodium high-temperature furnace into a copper block calorimeter.…”

“…4 [17] and the corresponding quantities for O 2 gas from JANAF thermochemical tables [18] with temperature is with in the uncertainty of the Gibbs energy data. High-temperature emf data of Alcock and Zador [2] with Ni + NiO reference [16] and Siemonsen [19] ) [14] ) and indirect (Southard and Shomate [16] ) experimental information Basic and Applied Research: Section I electrode shows systematic increase of DH o 298:15 with temperature, although the variation is only slightly larger than the error limit of Gibbs energy data. Their data obtained using Fe + Fe 1 -d O as reference electrode shows reasonably constant value for DH o 298: 15 .…”

“…5 for comparison. Siemonsen [19] measured the enthalpy of formation of Table 4 Reassessed thermodynamic data for MnO [16] -385.10 (±0.5) Solution calorimetry AEAEAE AEAEAE Millar [12] AEAEAE AEAEAE 62.4 (±1.4) Heat capacity 70-300 K Todd and Bonnickson [13] AEAEAE AEAEAE 59.71 (±1.0) Heat capacity 55-298 K Shapiro et al [14] AEAEAE AEAEAE 59.02 (±0.4) Heat capacity 1-400 K Robie and Hemingway [20] -385.22 Assessment AEAEAE AEAEAE Wagman et al [21] -385. 22 Compilation 59.706 Compilation Knacke et al [22] -382.54 Compilation 58.994 Compilation Pankratz [4] -385. .…”

“…This requires the use of paraffin oil as promoter and also yields mixed product requiring some corrections. Southard and Shomate [16] measured the heat of formation of MnO at 298.15 K as -385.10 (±0.5) kJ mol -1 by solution calorimetry using 1.006 N sulfuric acid as the solvent. The limits of error were estimated as the sum of the average deviations from the mean of the heats of solution of Mn and MnO, plus 0.05% of the total energy measured, plus 10% of the correction for vaporization of water, plus ±38 J uncertainty in the enthalpy of formation of water.…”

“…The limits of error were estimated as the sum of the average deviations from the mean of the heats of solution of Mn and MnO, plus 0.05% of the total energy measured, plus 10% of the correction for vaporization of water, plus ±38 J uncertainty in the enthalpy of formation of water. The value from combustion calorimetry by Siemonsen [19] is significantly more negative and that from solution calorimetry of Southard and Shomate [16] significantly more positive than values obtained from the third-law analysis. The results of the third-law analysis fall between those from combustion and solution calorimetry, but well outside the error limits of the calorimetric measurements.…”