The $1^{\text {st }}$ ionization enthalpy for Mg is $+737 \mathrm{~kJ} / \mathrm{mol}$. The most probable estimated value of the $2^{\text {nd }}$ ionization enthalpy of Mg is $\_\_\_\_$ .

The electronegativity of a group 13 element ' E ' is same as that of Ge (on Pauling scale and upto one decimal point). The CORRECT statements about $\mathrm{E}^{3+}$ are

A. It can act as a reducing agent.

B. It can act as an oxidizing agent.

C. $\mathrm{E}^{3+}$ is more stable than $\mathrm{E}^{+}$.

D. The standard electrode potential value for $\mathrm{E}^{3+} / \mathrm{E}$ is positive.

Choose the correct answer from the options given below :

Pairs of elements with the same number of electrons in their respective 4f orbital are

[Atomic number. Eu-63, Gd-64, Dy-66, Ho-67, Tm-69, Yb-70, Lu-71, Hf-72]

A. (Eu and Gd)

B. (Dy and Ho)

C. ( Yb and Hf )

D. ( Lu and Tm)

Choose the correct answer from the options given below :

Consider the metal complexes $\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}(\mathrm{A}),\left[\mathrm{NiCl}_4\right]^{2-}(\mathrm{B})$ and $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+}(\mathrm{C})$. Choose the CORRECT option by considering the number of unpaired electrons present in (A), (B) and (C) respectively and the order of frequency of absorption.