d and f BLOCK ELEMENTS

Why is the +3 oxidation state relatively unstable for Iron (Fe) in aqueous solution compared to +2?

• Fe3+ has a larger ionic radius than Fe2+
• Fe3+ is more hydrated than Fe2+
• Fe3+ is less soluble than Fe2+
• The high third ionisation energy required to form Fe3+ from Fe2+

Which of the following statements correctly describes the relationship between E° values and the oxidising/reducing nature of metal ions?

• A low negative E°(M3+/M2+) indicates a strong oxidising agent (M3+)
• A high positive E°(M2+/M) indicates a strong reducing agent (M)
• A low negative E°(M2+/M) indicates a strong oxidising agent (M2+)
• A high positive E°(M3+/M2+) indicates a strong oxidising agent (M3+)

Why is the E°(M2+/M) value for Vanadium (V) more negative than expected from the simple trend?

• The exceptional stability of the d3 configuration in V2+
• Its high melting point
• Its low atomic mass
• The relatively low sum of the first and second ionisation enthalpies of V

What is the primary factor that determines whether a first-row transition metal will react with 1M H+ ions?

• The metal's melting point
• The metal's density
• The metal's position in the periodic table
• The sign and magnitude of the metal's E°(M2+/M) value

Why is the E°(M3+/M2+) value for Iron (Fe) less positive than that for Cobalt (Co)?

• Fe3+ is smaller than Co3+
• Fe3+ has a higher charge density
• Fe2+ is more stable than Co2+
• Fe3+ (d5) is less stable than Co3+ (d6) relative to their M2+ states