Concept:Unsaturated hydrocarbons like naphthalene have a high carbon-to-hydrogen ratio, which leads to incomplete combustion, producing a yellow, sooty flame.
Explanation:Naphthalene is an unsaturated compound.
In unsaturated hydrocarbons, the proportion of carbon is larger than in saturated ones, meaning the carbon-to-hydrogen ratio is high.
During combustion, the large amount of carbon cannot be fully oxidized due to limited oxygen supply.
This incomplete combustion leaves unburnt carbon particles.
These hot carbon particles emit yellow light, making the flame appear yellow and sooty.
Even saturated hydrocarbons can produce a sooty flame if the air supply is restricted, confirming that incomplete combustion is the direct cause.
Excess air (Option C) would give a clean blue flame.
Impurities of nitrogen or sulfur (Option D) are not responsible for the sooty nature.
A low carbon-to-hydrogen ratio (Option A) would reduce soot, not increase it.
Answer:Option B: There is incomplete combustion.