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
4. the residue?
Equetion for reaction Pb(NO3)2----> PbO + O2 + NO2 (1) Pb(NO3)2 (2) NO2 (3) O2 (4) PbO
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
1. The compound is likely potassium chlorate (KClO3), which decomposes upon heating.
2. The reddish fume is likely chlorine gas (Cl2), which is released during the decomposition of potassium chlorate.
3. The gas that relights a glowing splint is likely oxygen gas (O2), which is also released during the decomposition of potassium chlorate.
4. The reddish-brown residue when hot and yellow residue when cold is likely a mixture of potassium chloride (KCl) and potassium perchlorate (KClO4). The heat causes potassium chlorate to react with the container, forming potassium chloride, while the cooling causes the formation of potassium perchlorate.
To determine the answers to these questions, we need to analyze the observations given.
1. The compound: The crackling sound, reddish fume, and gas that relights a glowing splint indicate that the compound is most likely a metal carbonate or a metal bicarbonate. On heating, carbon dioxide gas (CO2) is evolved, which is responsible for relighting the glowing splint. The gas produced confirms the presence of carbonates or bicarbonates.
2. The fume: The reddish fume is produced when a compound containing a metal is heated. It is likely to be a metal oxide or a metal salt that contains oxygen. Since the fume is reddish, it implies the presence of a metal that imparts a reddish color to the compound when heated. This metal could be copper (Cu).
3. The gas: The gas evolved that relights a glowing splint is most likely carbon dioxide (CO2). When carbonates or bicarbonates decompose upon heating, they release carbon dioxide gas, which has the ability to reignite a glowing splint.
4. The residue: The residue left behind after heating can provide some clues about the compound. The reddish-brown color when hot and yellow color when cold suggests the presence of a metal oxide. Copper oxide (CuO) is a common example that matches these observations.
In conclusion:
1. The compound is likely a metal carbonate or metal bicarbonate.
2. The reddish fume indicates the presence of a metal that imparts a reddish color when heated, possibly copper.
3. The gas evolved is most likely carbon dioxide (CO2).
4. The residue is likely copper oxide (CuO).