Standard molar Gibbs energy of formation of UTeO5(s) by the electrochemical method

✍ Scribed by Z. Singh; S. Dash; K. Krishnan; R. Prasad; V. Venugopal

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 136 KB
• Volume: 31
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1998.0434

✦ Synopsis

Standard molar Gibbs energies of formation of UTeO 5 (s) have been determined by measuring the relative oxygen chemical potential over the three phase system {U 3 O 8 (s) +TeO 2 (s) + UTeO 5 (s)} in the temperature range (821 to 993.5) K using a solid electrolyte galvanic cell having a 0.15 mole fraction calcia-stabilized zirconia (CSZ) as an electrolyte. The cell used was:

The observed e.m.f. values are represented by: (E ±1•10 -3 )/V = 0.7677-6.290•10 -4 (T /K).

The relative oxygen chemical potential over the three phase system was evaluated from the e.m.f. values and is given as: { µ(O 2 ) ± 1.4}/(kJ•mol -1 )=-759.8+0.4222 (T /K).

The standard molar Gibbs energies of formation of UTeO 5 (s) are evaluated from the oxygen chemical potential data, and the f G o m (T ) of U 3 O 8 (s) and TeO 2 (s) from literature. The resulting standard molar Gibbs energies of formation of UTeO 5 (s) are given by: { f G o m (UTeO 5 , s, T ) ± 4.6}/(kJ•mol -1 ) = -1642.5 + 0.4784 (T /K). Using the literature values, the f H o m (UTeO 5 , s, 298.15) has been calculated by using the second-and third-law methods. The resulting values are {-(1638.8 ± 9) and -(1601.6±10)} kJ•mol -1 , respectively.