Question

Which amongst the following is not a free state of carbon?
(A) Diamond
(B) Graphite
(C) Coke
(D) Petrol

Answer 1

Hint: Carbon is known to occur in free state as well as combined state. Allotropes are crystalline in structure and have free state in nature. Carbon, when combined with methane and carbon dioxide, show combined forms.

Complete answer:
- Free state is the property of an element that does not require it to be combined with other elements or being chemically bonded with them.
- Other than carbon, the oxygen molecule also shows properties of being in free state.
- Carbon exists in free state as well as combined state.
- Allotropes of carbon such as diamond, graphite, and coal occur in free state. On the other hand, the combined forms of carbon exist in the form of compounds in different states (liquid, solid, and gas) such as petroleum.
- Coke is nearly pure carbon which is formed by heating coal in vacuum.

Therefore, the correct answer is (D) Petrol.

Additional Information: Carbon is present in almost everything around us. Humans, to some extent, are made of carbon. It is present in the air we breathe, clothes we wear. Carbon does not melt under normal conditions; it goes under the process of sublimation.

Note: Diamond, Graphite, and Coke are all known to be allotropes carbon. Whereas, Petrol on the other hand being an energy rich fuel is made up by combining carbon dioxide from air and hydrogen.