| Popis: |
A high-precision drop-calorimetric system has been used to measure the enthalpy (relative to 298.15 K) of Na 2 O in the temperature range 500 to 1300 K. A rapid rise in the derived C p ( T ) is observed about 900 K, which may be attributed to the onset of a diffuse transition in Na 2 O and a disordering of the Na + ions. The results are therefore represented by two equations, one for temperatures below 900 K and another for temperatures above 900 K. In the range 298 to 900 K: { H o ( T ) − H o ( 298.15 K ) } / c a l t h m o l − 1 = 13.8814 ( T / K ) + 4.4249 × 10 − 3 ( T / K ) 2 − 4532.09. In the range 900 to 1300 K: { H o ( T ) − H o ( 298.15 K ) } / c a l t h m o l − 1 = 35.4157 ( T / K ) − 2.80046 × 10 − 2 ( T / K ) 2 + + 1.42549 × 10 − 5 ( T / K ) 3 − 8036.87. All temperatures are based on IPTS-68. Values of { H o ( T )− H o (298.15 K)}, C o p ( T ), { S o ( T ) − S o (298.15 K)}, Δ H o f ( T ), Δ G o f ( T ), and log K o p ( T ) are tabulated. |
