The chemical name of borax is

Select the incorrect statement:
$a$. $PCl_5$ forms a weak monobasic acid during hydrolysis.
$b$. In $B_3N_3H_6$,nucleophilic attack occurs on the $B$ atom.
$c$. $Al_2Cl_6$ is a polar and planar molecule.
$d$. In $AlF_3$,the hybridization of $Al$ is $sp^2$.

In group $13$ of the long form of the periodic table,an element $X$ has a boiling point of $T_2 \ (K)$ and a melting point of $T_1 \ (K)$. Identify the element $X$ for which $T_2 - T_1 \ (K)$ is maximum.

In the reactions $I$ and $II$,the covalencies of $Be$ and $Al$ in $X$ and $Y$ are respectively:
$I$ $Be(OH)_2 + NaOH \text{ (excess)} \rightarrow X$
$II$ $Al(OH)_3 + NaOH \text{ (excess)} \rightarrow Y$

Two elements $X$ and $Y$ react with highly electropositive metals to form binary compounds,which upon hydrolysis yield borane and silane,respectively. What are $X$ and $Y$?

Which of the following element$(s)$ exist in the liquid state?