Question

The allotrope of carbon formed when hydrocarbons are burnt in limited supply of air is:

• A. Charcoal
• B. Carbon black
• C. Coke
• D. Graphite

Hint:

Limited oxygen supply leads to soot (carbon black) formation.

Answer 1

The Correct Option is B

Step 1: Defining incomplete combustion.
Burning hydrocarbons with insufficient oxygen prevents full conversion to CO₂, instead generating fine carbon particulates.

Step 2: Naming the product.
These finely divided carbon particles are called carbon black or soot.

Step 3: Differentiating other carbon forms.
Charcoal and coke arise from destructive distillation, not direct burning; graphite is a naturally occurring crystalline allotrope.

Step 4: Selecting the correct option.
Incomplete combustion specifically yields carbon black.

Step 5: Conclusion.
The correct answer is carbon black.