Explain what happens when boric acid is heated.

Boron trifluoride on reaction with lithium aluminium hydride in ether gives $LiF$, $AlF_3$ and $X$. $X$ on reaction with $NH_3$ gives $Y$. $Y$ on further heating gives a compound $Z$. The number of $\sigma$-bonds and $\pi$-bonds in $Z$ are $x$ and $y$ respectively. $(x+y)$ is equal to

What is the molecular formula of borazole?

When $AlCl_3 \cdot 6H_2O$ is strongly heated,then it forms

Given below are two statements:
Statement $I$: Aluminium is more electropositive than thallium as the standard electrode potential value of $E^\circ_{Al^{3+}/Al}$ is negative and $E^\circ_{Tl^{3+}/Tl}$ is positive.
Statement $II$: The sum of first three ionization enthalpies of boron is very high when compared to that of aluminium. Due to this reason, boron forms covalent compounds only and aluminium forms $Al^{3+}$ ion.

Which of the following does not liberate $H_2$ gas upon reaction with an acid?