Which of the following species has the greatest reducing power based on standard Gibbs free energy of formation (ΔG°f) values?

• A. Li (s)
• B. Cu2+ (aq)
• C. Ag+ (aq)
• D. Fe2+ (aq)

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of reducing power. Reducing power refers to the ability of a species to donate electrons in a redox reaction. A species with greater reducing power will have a more negative standard Gibbs free energy of formation (ΔG°f) for its oxidation reaction.
2. Step 2: Recall the relationship between Gibbs free energy and the standard electrode potential (E°). The equation ΔG° = -nFE° connects Gibbs free energy (ΔG°) to the standard electrode potential (E°), where n is the number of electrons transferred, F is the Faraday constant, and E° is the standard electrode potential. A more negative ΔG° corresponds to a higher E° for reduction reactions.
3. Step 3: Compare the standard Gibbs free energy of formation (ΔG°f) values for the given species. For each species, determine the ΔG°f value associated with its oxidation reaction (e.g., Li(s) → Li⁺ + e⁻). The species with the most negative ΔG°f value will have the greatest reducing power.
4. Step 4: Analyze the chemical nature of the species. Metals like Li(s) are typically strong reducing agents because they readily lose electrons to form cations. Compare this behavior with the other species (Cu²⁺, Ag⁺, Fe²⁺), which are ions and generally act as oxidizing agents rather than reducing agents.
5. Step 5: Conclude that Li(s) has the greatest reducing power based on its chemical properties and the expected ΔG°f values. This conclusion aligns with the fact that alkali metals like lithium are known for their strong reducing capabilities.