Which of the following complex ions does not exist?

Explain what happens when boric acid is heated.

What are $X$ and $Y$ respectively in the following reactions?
$X \xleftarrow{CO} B_2 H_6 \xrightarrow[(C_2 H_5)_2 O]{NaH} Y$

$A$ 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.

Which base among the following reacts with diborane to cleave it unsymmetrically?

Common alum is