Question

Which of the following statement(s) is/are true?

• A. $Z{r}^{4+}\text{and}H{f}^{4+}$ posses almost the same ionic radii.
• B. Mixed oxides of lanthanoids are employed as catalysts in petroleum cracking
• C. $C{e}^{4+}$ can act as an oxidizing agent
• D. Common oxidation state of Pr, Nd, Tb and Dy is +4 state

Answer 1

Answer: (A), (B), (C)

$C{e}^{4+}$ can act as an oxidizing agent

As a result lanthanide contraction $Z{r}^{4+}\text{and}H{f}^{4+}$ possess almost the same ionic radii. $C{e}^{4+}$ is an oxidising agent.
$C{e}^{4+}$ gains electron acquire more stable $C{e}^{3+}$ state. Thus it act as good analytical agent.
$C{e}^{4+}+e^{-}\to C{e}^{3+};E^o=+1.74V$
Pr, Nd, Tb and Dy also ​exhibit +4 state but ​only in oxides $\left(M{O}_2\right)$

Mixed oxides of lanthanoids are employed as catalysts in petroleum cracking​.

Hence, statements (b), (c) and (d) are correct.

​