Question

Thermodynamically, in which form of carbon is the most stable?
A.Coal
B.Fullerenes
C.Diamond
D.Graphite

Answer 1

Hint: The form of carbon that is most stable is mixed with the lead and used in pencils. It is a soft substance and is used as a lubricant. It has a layered structure.

Complete step by step answer:
Carbon exists in various allotropes. Allotropes are those which have different structures but are made up of only one element. The commonly known allotropes of carbon are diamond and graphite. There is one more allotrope of carbon that is known as buckminsterfullerene. Let us look at each of the allotrope of carbon:
Diamond is very well known to us. It is extremely hard and is used in making jewelry and glass cutters. Diamond is the hardest natural substance known no other natural substance can cut diamond except diamond itself.
Graphite is another allotrope of carbon graphite is an electrical conductor unlike diamond. It is used in electric lamps and electrodes. Under standard condition graphite is the most stable allotrope of carbon. That is why it is used as a standard for calculation of heat of formation for carbon compounds.
Amorphous carbon is called coal, suit and carbon black. They are produced by pyrolysis or decomposition in the presence of heat.
Buckminsterfullerene was discovered in 1985. It resembles a kind of football. Since it is an allotrope of carbon it is entirely made of carbon only. The chemical and physical properties of buckminsterfullerene are still under consideration. They are mainly used for medical use.

Hence, the correct option is option D.

Note:
The Powder of graphite is used as a lubricant. It does not burn readily even at high temperatures. It is used in high temperature crucible for melting metals and also used in nuclear reactors. At very high temperature and pressure around 2000 degree Celsius and 5 GPa it gets converted into diamond, but the process of conversion of graphite to diamond is very slow.