d and f BLOCK ELEMENTS

Which of the following best explains the relatively low E°(M3+/M2+) value for Chromium (Cr)?

• The instability of the d4 configuration of Cr2+
• The high hydration energy of Cr3+
• The relatively stable d3 configuration of Cr3+ compared to Cr2+
• The low third ionisation energy of Cr

Why are the E°(M3+/M2+) values generally higher (more positive) for the later members of the first transition series compared to the earlier ones?

• Later metals have lower atomic radii
• Later metals prefer lower oxidation states
• Later metals have higher third ionisation energies due to increased nuclear charge
• The hydration enthalpies decrease across the series

What is the consequence of a metal having a negative E°(M2+/M) value when placed in 1M HCl?

• It will form a passive oxide layer
• It will not react at all
• It will generally dissolve, producing hydrogen gas
• It will only dissolve if heated

Which of the following best describes the trend in reducing strength for the ions Ti2+, V2+, Cr2+, and Fe2+ based on their E°(M3+/M2+) values?

• Fe2+ > Cr2+ > V2+ > Ti2+
• Cr2+ > Ti2+ > V2+ > Fe2+
• Ti2+ > V2+ > Cr2+ > Fe2+
• Ti2+ = V2+ = Cr2+ = Fe2+

Why is the +2 oxidation state common and stable for most first-row transition metals?

• It involves gaining electrons to fill the d subshell
• It is the only oxidation state possible
• It involves the loss of the relatively higher energy 4s electrons and one or two 3d electrons
• It requires the least amount of energy overall