A compound on heating gives a crackling sound, a reddish fume, and a gas which relights a glowing splint. the residue is reddish brown when hot and yellow when cold. What are- 1. the compound? 2. the fume 3. the gas

Question

4. the residue?

Answer 1

Not much to go on here.
My best guess is
compound is Hg(NO3)2
fume is NO2
gas is NO2 AND O2
residue is HgO/Hg(NO3)2/Hg mixture although the Hg may be driven off at an elevated temperature.

HgO is the right color at the two temperatures (hot and cold), NO2 is reddish-brown fume, O2 will relight an extinguished glowing splint.

Hg(NO3)2 --> HgO + NO2 step 1
2HgO ==> 2Hg + O2 step 2

Answer 2

Equetion for reaction Pb(NO3)2----> PbO + O2 + NO2 (1) Pb(NO3)2 (2) NO2 (3) O2 (4) PbO