WAEC - Chemistry (2001 - No. 27)
Benzene produces more soot than ethene on burning because benzene
has a higher molar mass
has a higher degree of unsaturation
undergoes substitution and addition reactions
is a liquid at room temperature
Paliwanag
Benzene has a higher carbon content than other saturated hydrocarbons, like ethene. This invariably means it has a higher molar mass. When benzene burns, it forms elementary carbon, which causes it to burn with a sooty flame. Benzene is a member of the aromatic hydrocarbon family, which are nonpolar molecules that are usually colourless liquids or solids.