Exercises
237
2. Calculate ∆E at 1 000 K.
Data
Standard enthalpy of formation of H 2 O (g) : ∆ f H ° 1000 K = − 247.9 kJ mol
−1
Standard entropy of formation of H 2 O (g) : ∆ f S ° 1000 K = − 55.3 J mol
−1
 K
−1
Percent of oxygen in air: 21%
3. How does the emf ∆E T vary with temperature when the battery is supplied
with the following fuels:
2 hydrogen H 2 ,
2 methane CH 4 ,
2 methanol CH 3 OH.
4. Determine the thermodynamic efficiency of the cell at 1 000 K in the following cases:
2 with H 2 as fuel,
2 total oxidation of CH 4 with oxygen.
Data
Enthalpy and free molar enthalpy of complete oxidation of the following fuels at 1 000 K:
Fuel
∆ r H [kJ mol
−1
]
∆ r G [kJ mol
−1
]
H 2
− 247.9
− 192.6
CH 4
− 800.5
− 800.2
5. Figure 98 shows the ionic conductivity in Arrhenius coordinates of several
oxide ion conducting electrolytes.