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

What is added to borax to obtain boric acid?

$A$ black coloured element with $ns^2 np^1$ outer electronic configuration cannot react with air in its crystalline form. However, in amorphous form, it gives an oxide in air which is acidic in nature. Identify the element.

The number of acidic protons in $H_{3}PO_{3}$ is:

The geometry around boron in the product '$B$' formed from the following reaction is
$BF_{3} + NaH \xrightarrow{450 \ K} A + NaF$
$A + NMe_{3} \rightarrow B$

The correct Lewis acidity order of $BX_3$ is: