Which one of the following metallic oxides exhibits amphoteric nature?

When $AlCl_3 \cdot 6H_2O$ is strongly heated,then it forms

The number of acidic protons present in $H_3PO_2$,$H_3PO_3$ and $H_3PO_4$ respectively,are .....

$2BF_3 + 6NaH \xrightarrow{450 \ K} X_{(g)} + 6NaF$. Which of the following statements is \textbf{Incorrect} for $X$?

Which of the following reactions can be used to prepare diborane?
$I. BF_3 + LiAlH_4 \xrightarrow{\text{ether}}$
$II. BF_3 + NaH \xrightarrow{450 \ K}$
$III. Na_2B_4O_7 + H_2O \longrightarrow$
$IV. NaBH_4 + I_2 \longrightarrow$

If the formula of Borax is $Na_2B_4O_x(OH)_y \cdot zH_2O$,then $x+y+z = ...........$.