Question #44897

Consider the following statements regarding the chemistry of f-block elements and their consequences:

I. Mischmetal is an alloy comprising $\sim 50\%$ $\ce{Ce}$, $\sim 25\%$ $\ce{La}$, along with $\ce{Nd}$, $\ce{Pr}$, and $\sim 5\%$ $\ce{Fe}$, widely used in $\ce{Mg}$-based alloys for lighter flints. II. The post-lanthanoid transition metals $\ce{Zr}$ and $\ce{Hf}$ possess nearly identical atomic radii ($160\text{ pm}$ and $159\text{ pm}$ respectively) primarily due to the poor shielding effect of $4f$ electrons. III. The basicity of lanthanoid hydroxides, $\ce{Ln(OH)3}$, increases from $\ce{La(OH)3}$ to $\ce{Lu(OH)3}$ due to the increase in covalent character of the $\ce{Ln-OH}$ bond. IV. The separation of $\ce{Zr(IV)}$ and $\ce{Hf(IV)}$ is highly challenging because their identical principal quantum numbers for the valence d-orbitals lead to identical hydration enthalpies. V. The third ionization enthalpy ($IE_3$) of $\ce{Eu}$ is anomalously high because the third electron must be removed from a highly stable, half-filled $4f^7$ subshell.

Determine the total number of correct statements.