A research team needs a portable power source whose overall standard free-energy change is approximately −350 kJ for each mole of overall reaction as written. They have access only to the aqueous ions and gases listed below, each at standard conditions. Faraday’s constant is 9.65 × 10⁴ C mol⁻¹.
Standard reduction potentials (25 °C):
(a) Choose one species from the list to be reduced and one different species to be oxidized so that the overall galvanic cell reaction will have a standard free-energy change as close as possible to −350 kJ mol⁻¹ (per mole of reaction as finally written). Justify your selection quantitatively.
(b) Balance each selected half-reaction for mass and charge, including electrons, and combine them to obtain the overall redox reaction. Clearly indicate the number of electrons transferred n in the balanced overall equation.
(c) Using your balanced reaction from part (b), calculate the standard free-energy change ΔG° (in kJ mol⁻¹). Show all work, including calculation of the corresponding E°cell.
(d) Suppose the researchers need to scale the cell so that it releases exactly −700 kJ of free energy per complete discharge. Determine the stoichiometric amount (in moles) of overall reaction that must occur to meet this energy requirement. Explain your reasoning.