Mention the isotopes of boron.

$Na_2B_4O_7$ $\xrightarrow{x} H_3BO_3$ $\xrightarrow{\Delta} B_2O_3$ $\xrightarrow{y} B$
Here $X$ and $Y$ are respectively:

Which of the following substances imparts a green color to the burner flame?

Which of the following is not correct regarding Orthoboric acid $(H_3BO_3)$?

Which of the following is the correct decreasing order of Lewis acid strength of boron halides?

$A$ 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. $H_{2}SO_{4}$ is added to a hot solution of $X,$ white crystals of an acid $Z$ separate out.
Write equations for all the above reactions and identify $X, Y,$ and $Z$.