The main product obtained when a solution of sodium carbonate reacts with mercuric chloride is

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

Bleaching powder is a compound having the molecular formula

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 :-

Which of the following compounds decompose on heating?

Holme's signals can be obtained by using