Question

When the diamond is heated at $1800 - {2000^ \circ }C$ in a vacuum, it converts into:
A.Graphite
B.Coke
C. $C{O_2}$
D. $CO + C{O_2}$

Answer 1

Allotropy is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure.

Complete step by step answer:
Graphite is the most stable allotrope of carbon.
All allotrope of carbon turn into graphite at higher temperatures.
Diamond also turns into graphite at a temperature between $1800 - {2000^ \circ }C$
Under normal conditions, diamond is metastable, meaning that it converts back to graphite when the process is initiated with sufficient energy.
It can switch its internal structure to a different order, thereby turning into graphite.
The allotropes of carbon are as shown:

Hence, option A is correct.

Note:
Diamond is harder than graphite because in diamond, each carbon atom forms $4$covalent bonds in a tetrahedral structure. The sheets of carbon become bonded by weaker intermolecular forces. It is because of these weak intermolecular forces that the layers of graphite can slide over each other, making the overall substance a lot weaker than diamond.