Which of the following mixtures is known as fusion mixture?

Which of the following does not dissolve in dil $H_2SO_4$?

Copper is very slowly oxidized on the surface in moist air,giving a green coating of verdigris. The chemical formula of verdigris is:

Identify the reactions in which,upon heating,a diatomic gas is evolved,leaving behind a metallic residue.
$(A)$ $2NaN_{3(s)} \xrightarrow{\Delta} 2Na_{(s)} + 3N_{2(g)}$
$(B)$ $Ni(CO)_{4(g)} \xrightarrow{250^{\circ}C} Ni_{(s)} + 4CO_{(g)}$
$(C)$ $2KClO_{3(s)} \xrightarrow{\Delta} 2KCl_{(s)} + 3O_{2(g)}$
$(D)$ $2HgO_{(s)} \xrightarrow{\Delta} 2Hg_{(l)} + O_{2(g)}$
$(E)$ $NH_{4}NO_{2(s)} \xrightarrow{\Delta} N_{2(g)} + 2H_{2}O_{(g)}$

Match the following items in Column-$I$ with the corresponding items in Column-$II$.

Column-$I$	Column-$II$
$I$. $Na_2CO_3 \cdot 10H_2O$	$A$. Portland cement ingredient
$II$. $Mg(HCO_3)_2$	$B$. Castner-Kellner process
$III$. $NaOH$	$C$. Solvay process
$IV$. $Ca_3Al_2O_6$	$D$. Temporary hardness

Which of the following pairs of atomic numbers represents elements belonging to the $s$-block?