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

Select the correct statement :-
$(a)$ $CaSO_4 \cdot 2H_2O \xrightarrow{393 \ K} CaSO_4 \cdot \frac{1}{2}H_2O + \frac{3}{2}H_2O$
$(b)$ $3Br_2 + 6NaOH \xrightarrow{\text{hot & conc.}} 5NaBr + NaBrO_3 + 3H_2O$
$(c)$ $3Mg + N_2$ $\rightarrow Mg_3N_2$ $\xrightarrow{6H_2O} 3Mg(OH)_2 + 2NH_3 \uparrow$
$(d)$ $2Be + C$ $\rightarrow Be_2C$ $\xrightarrow{4H_2O} 2Be(OH)_2 + CH_4 \uparrow$
Correct answer is :-

$A$ pink colored salt on dry heating becomes blue in colour. The salt may contain:

Match the following columns:

Column-$I$	Column-$II$
$(i)$ Solvay process	$(p)$ $Na_2O$
$(ii)$ Evolve $CO_2$ on heating	$(q)$ $Na_2O_2$
$(iii)$ Aqueous solution is not neutral towards litmus	$(r)$ $NaHCO_3$
$(iv)$ Used as air purifier in submarine	$(s)$ $Na_2CO_3$

The compound which gives off oxygen on moderate heating is

Which of the following conduct electricity in the fused state?