Question

A hydrocarbon compound burns with a non-luminous flame. Which hydrocarbon type does it indicate?
(A) Alicyclic hydrocarbon
(B) Aromatic hydrocarbon
(C) Unsaturated hydrocarbon
(D) Acyclic hydrocarbon

Answer 1

Hint: The non-luminous flame is observed as the compound does not burn completely. The non-luminous flame is because of the soot particles present.

Step by step answer: The hydrocarbons that have closed ring structures and resemble the aliphatic or acyclic hydrocarbons in properties are known as alicyclic hydrocarbons. The alicyclic hydrocarbons are not aromatic. Thus, alicyclic hydrocarbons burn with a non-sooty or luminous flame.
Thus, option (A) is not correct.

The hydrocarbons that have conjugated planar ring systems along with delocalized pi-electron clouds are known as alicyclic hydrocarbons. The aromatic hydrocarbons do not burn completely. Thus, burning of aromatic compounds produces sooty flame. The sooty flame is due to the presence of carbon in the flame. Thus, aromatic hydrocarbons burn with a sooty or non-luminous flame.
Thus, option (B) is correct.

The hydrocarbons that have double or triple covalent bonds between the adjacent carbon atoms are known as unsaturated hydrocarbons. The unsaturated hydrocarbons are not aromatic. Thus, unsaturated hydrocarbons burn with a non-sooty or luminous flame.
Thus, option (C) is not correct.
The hydrocarbons that have open chain structures and do not form a ring are known as acyclic hydrocarbons. The acyclic hydrocarbons are not aromatic. Thus, acyclic hydrocarbons burn with a non-sooty or luminous flame.
Thus, option (D) is not correct.

Thus, a hydrocarbon compound that burns with a non-luminous flame indicates that it is an aromatic hydrocarbon. Thus, the correct option is (B) aromatic hydrocarbon.

Note: The flame test is used as a test to distinguish between aliphatic and aromatic hydrocarbons. If a luminous flame is observed then it is an aliphatic hydrocarbon and if non-luminous flame is observed then it is an aromatic hydrocarbon.