System Zn–Rh–O: heat capacity and Gibbs free energy of formation using differential scanning calorimeter and electrochemical cell

• Published in: Journal of solid state electrochemistry 2009-08, Vol.13 (8), p.1201-1207
• Main Authors: Banerjee, Aparna, Singh, Ziley
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Original Paper; Physical Chemistry
• ISSN: 1432-8488; 1433-0768
• DOI: 10.1007/s10008-008-0645-9

The standard molar Gibbs free energy of formation of ZnRh 2 O 4 (s) has been determined using an oxide solid-state electrochemical cell wherein calcia-stabilized zirconia (CSZ) was used as an electrolyte. The oxide cell can be represented by: . The electromotive force was measured in the temperature range from 943.9 to 1,114.2 K. The standard molar Gibbs energy of formation of ZnRh 2 O 4 (s) from elements in their standard state using the oxide electrochemical cell has been calculated and can be represented by: . Standard molar heat capacity C o p,m ( T ) of ZnRh 2 O 4 (s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges, from 127 to 299 and 307 to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: . The heat capacity of ZnRh 2 O 4 (s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K.