Observe the following reactions (not balanced)

$$ \begin{aligned} & \mathrm{BF}_3+\mathrm{LiAlH}_4 \xrightarrow{\left(\mathrm{C}_2 \mathrm{H}_5\right)_2 \mathrm{O}} X+\mathrm{LiF}+\mathrm{AlF}_3{ }^{-} \\ & X+\mathrm{NaH} \longrightarrow Y \end{aligned} $$

The incorrect statement about $Y$ is

The dihedral angles in gaseous and solid phases of $\mathrm{H}_2 \mathrm{O}_2$ molecule respectively are

The hydrides of which group elements of the periodic table form electron precise hydrides?

Identify the correct statements about the hydrides.

I. In saline hydrides oxidation state of hydrogen is +1 .

II. La H is an example of interstitial hydride.

III. $\mathrm{NH}_3, \mathrm{H}_2 \mathrm{O}$ have the tendency to form hydrogen bonds.

IV. Electrolysis of molten sodium hydride liberates $\mathrm{H}_2$ gas at cathode.