The given reaction is the result of which process?
$Na_2CO_3 \cdot 10H_2O \xrightarrow[open]{air} Na_2CO_3 \cdot H_2O + 9H_2O$

Which of the following statements are correct for alkali metal compounds?
$(i)$ Superoxides are paramagnetic in nature.
(ii) The basic strengths of hydroxides increase down the group.
(iii) The conductivity of chlorides in their aqueous solutions decreases down the group.
(iv) The basic nature of carbonates in aqueous solutions is due to cationic hydrolysis.

The chemical formula of feldspar is

Give any two uses of washing soda.

On heating 'Trona $(Na_2CO_3 \cdot NaHCO_3 \cdot 2H_2O)$' with the help of a Bunsen burner,we get . . . . . . as the solid residue.

Identify the correct statements from the following :
$I$. Tendency to form halide hydrates gradually increases from $Be$ to $Ba$ down the group.
$II$. Tendency to form stable superoxides increases from $Li$ to $Cs$ down the group.
$III$. Low solubility of $LiF$ is due to its high lattice energy.
$IV$. Solubility of carbonates of group-$2$ elements increases down the group.