Boric acid,$H_3BO_3$,is a/an ....

Boron halides behave as Lewis acids because of their nature.

Which of the following is a non-metal?

Conc. $HNO_3$ can be stored in a container of

$TlI_3$ is isomorphous with:

Consider the following reactions (not balanced):
$BF_3 + NaH \xrightarrow{450 \ K} X + NaF$
$X + H_2O \longrightarrow Y + H_2 \uparrow$
The correct statements about $X$ and $Y$ are:
$I$. $X$ is an electron-deficient molecule
$II$. In $X$,$B-B$ bond is present
$III$. $Y$ is a weak tribasic acid
$IV$. $Y$ acts as a Lewis acid