Four separate chemical changes are listed below, each occurring at 298 K and 1 bar.
I. 2 H₂O(l) → 2 H₂(g) + O₂(g)
II. N₂(g) + 3 O₂(g) → 2 NO₃⁻(aq)
III. 6 CO₂(g) + 6 H₂O(l) → C₆H₁₂O₆(s) + 6 O₂(g)
IV. Cu²⁺(aq) + 2 e⁻ → Cu(s) (E∘=+0.34V)
For each process, assume standard-state conditions and that no additional reagents are present other than those explicitly written.
(a) For each reaction, predict the sign of ΔG∘ and briefly justify your choice using thermodynamic or electrochemical reasoning appropriate to the information given.
(b) Identify the most practical form of external energy (e.g., electrical, radiant (light), thermal) that could be supplied to drive each non-spontaneous process under laboratory conditions, and justify your selection for each case.
(c) Choose ONE of the non-spontaneous reactions from parts (a) and propose a realistic laboratory setup that could couple the necessary external energy to drive the reaction. In your description, explain how energy flows from the external source into the chemical system.