Chapter 10, Problem 10.5E

1) Using the half reaction data in Table 11.1), write balanced overall reactions for the following redox processes. Calculate the E°, peº and delataGº values for each overall reaction. Indicate whether each reaction is thermodynamically favorable under standard conditions. i) Oxidation of Mn2+ to MnO2(s) using 12(aq) to form I-. ii) Oxidation of Pb(s) to Pb2+ by Zn²+ to form Zn(s). iii) Oxidation of acetate (CH3COO¯) to CO2 by SO4²¯ to form HS¯. 7 ·H+ + e¯ ½-½ >> CH, COO¯ + 1 H₂O E° = 0.075 V

2) Chlorinated solvents such as carbon tetrachloride (CCI4) can be degraded in a process called reductive dechlorination where Cl atoms are removed and replaced with H atoms. For example: CCl4 + H+ +2е¯ CHCl3 + CI Eº = 0.67 V In the process of in situ bioremediation an electron donor such as acetate (CH3COO¯) is typically added and is oxidized to provide the electrons for the reduction of CCl4. In groundwater devoid of oxygen, nitrate typically serves as the electron acceptor. Answer the questions below using thermodynamics data and that provided above. i) Can CCl4 could serve as an electron acceptor for acetate? ii) Which electron acceptor, CCl4 or NO3, would be thermodynamically preferred? iii) What do the results in i and ii imply for remediation in an aquifer that also contains nitrate?

Problem 4.3 A thermal power plant plans to replace 20 vol.% of its natural gas by renewable hydrogen from a nearby facility. In its public announcement, the company claims a corresponding (20%) reduction in CO2 emissions, which has been challenged by an environmental group. Can you do necessary calculations to settle the issue and avoid possible public embarrassment for the company? (25) Problem 4.4 Explain the working principle of solid oxide electrolyzer with a suitable sketch and operating parameters. (20)