d and f BLOCK ELEMENTS

According to the text, why do Mn, Ni, and Zn have more negative E°(M2+/M) values than expected from the general trend?

• Because they have lower ionization enthalpies than their neighbors.
• Because they have higher hydration enthalpies than their neighbors.
• Because they are less abundant than their neighbors.
• Because their M2+ ions achieve particularly stable electronic configurations (d5, d8/d10, d10) not fully accounted for by simple thermochemical calculations.

What general trend is observed for E°(M2+/M) values across the first transition series (Sc to Zn) as mentioned in the text?

• A general trend towards more negative E° values across the series.
• A general trend towards increasingly positive E° values across the series.
• A general trend towards increasingly negative E° values across the series.
• A general trend towards less negative E° values across the series.

Why is Mn3+ considered an oxidizing agent according to the text?

• Because it readily loses electrons to achieve a d3 configuration.
• Because the d4 configuration is inherently unstable.
• Because its configuration changes to the less stable d6 configuration upon gaining an electron.
• Because the change from Mn3+ (d4) to Mn2+ (d5) results in the highly stable half-filled d5 configuration.

Why is Cr2+ considered a reducing agent according to the text?

• Because it readily gains electrons to achieve a d6 configuration.
• Because the d4 configuration is inherently unstable.
• Because its configuration changes to the more stable d5 configuration upon losing an electron.
• Because its electronic configuration changes from d4 to d3, achieving a more stable half-filled t2g level.

What is the significance of the comparison between observed and calculated E° values shown in Fig. 4.4?

• It proves that the thermochemical parameters are completely inaccurate.
• It shows that calculated values are always more accurate than observed values.
• It confirms that the simple thermochemical model perfectly predicts all E° values.
• It reveals deviations from the simple thermochemical model, indicating additional factors like electronic configuration stability influence the E° values.