Question

Assertion: Graphite is soft while diamond is hard.
Reason: Graphite has a three-dimensional structure while diamond has planar structure.
A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B) Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion
C) Assertion is correct but Reason is incorrect
D) Assertion is incorrect but Reason is correct

Answer 1

Allotropes are the forms of the same element having different chemical and physical properties. Elements like carbon, sulfur, phosphorus, oxygen exhibit the allotropes. The differences in the structure of the allotropes give rise to the difference in their properties of the allotropes even if they are made up of the same element.

Complete step-by-step answer:
Graphite is one of the allotropes of the carbon in which each carbon is sp2 hybridized attached to three other carbon atoms. In graphite, the hexagonal rings formed by the carbon forms the layer structure.
These layers of graphite are linked to each other by the weak van der Waals forces of attraction between the layers hence, it is easy to cut the graphite and it is soft.

Diamond exhibits cubic crystal structure with each carbon is tetrahedrally linked to four other carbon atoms and forms the 3D structure. These carbons are linked to each other by the strong force of attraction hence, the diamond is rigid.

Here, Assertion is given as Graphite is soft while diamond is hard is correct. Here, the reason given is Graphite has a three-dimensional structure while the diamond has a planar structure is incorrect.

Here, option (A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion is the incorrect option.

Now, option (B) Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion is the incorrect option.
Option(C) Assertion is correct but Reason is incorrect, it is the correct answer for the given question.
Option(D) Assertion is incorrect but Reason is correct, it is an incorrect answer.

Hence the correct answer is option ‘C’.

Note: Diamond, Graphite, Graphene, fullerenes, carbon nanotubes are the allotropes of the carbon.All these are different forms of carbon and possess different physical and chemical properties mainly depending on their structures. The forces of attraction between the atoms of the allotropes diced its nature. The stronger the force, the more rigid is the compound while the weaker is the forces softer is the compound.