$BCl_3$ and $AlCl_3$ exist in $:-$

The most acidic of the following compounds is

Which of the following is a true alum?

$A$ certain salt $X$ gives the following results:
$(i)$ Its aqueous solution is alkaline to litmus.
$(ii)$ It swells up to a glassy material $Y$ on strong heating.
$(iii)$ When conc. $H_2SO_4$ is added to a hot solution of $X$,white crystals of an acid $Z$ separate out.
Identify $X, Y$ and $Z$ and write the equations for the reactions.

Aluminium hydroxide is soluble in excess of sodium hydroxide forming the ion

Explain the following:
$(1)$ Gallium has higher ionisation enthalpy than aluminum.
$(2)$ Boron does not exist as $B^{3+}$ ion.