Question

Assertion :Diamond is the hardest substance on the earth.
Reason: It has high melting point.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

• Carbon has different allotropic forms like soot, charcoal, graphite, diamond etc. And diamond is the hardest among all. It is shining because of its lattice structure. It is less stable and has very few impurities, which makes it suitable for optical application. A considerably stronger force is required to break this bond. It is the arrangement of molecule of carbon which makes it difficult to break.
  
• Arrangement of carbon atoms in diamond is neither a heap of atoms like in charcoal nor layers like graphite. It has a three dimensional network of carbon atoms held together with a strong bond in all directions. These atoms are situated in different planes. It has extremely rigid lattice. Each atom of the carbon is shared with four other atoms. It forms a tetrahedral structure which is very rare. It is rare because it is formed only under massive pressure and high temperature.Hence,Diamond has high melting point.
  
• Hence both Assertion and Reason are correct but Reason is not correct explanation for Assertion.