Which among the following statements is not correct with respect to allotropes of Carbon?

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NDA General Ability Test 16 April 2023 Official Paper
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  1. Graphite is a good conductor of electricity.
  2. Diamond is the hardest substance known.
  3. Fullerene is one of the allotropes of carbon.
  4. Next to diamond, graphite is the second hardest known substance.

Answer (Detailed Solution Below)

Option 4 : Next to diamond, graphite is the second hardest known substance.
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Detailed Solution

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The correct answer is Next to diamond, graphite is the second hardest known substance.

Key Points

  • Allotropes of carbon:
    • Carbon allotropes refer to different well-defined structures of carbon-pure materials, in which carbon atoms are bonded in specific ways.
    • Carbon shows allotropic forms like Diamond, graphite, Fullerene.
      • Graphite:
        • Graphite is a good conductor of heat and electricity.
        • It is very soft and slippery and for this reason, graphite is used as a lubricant in the machine running at high temperatures, where oil cannot be used as a lubricant.
        • Every carbon atom in graphite is bonded to three other carbon atoms in such a way that a layered hexagonal structure is formed.
      • Diamond:
        • Diamond has a high density of 3.51 gm due to its three-dimensional giant structure.
        • It is a bad conductor of electricity.
        • Diamond is the hardest substance on earth.
        • It is used as an abrasive for sharpening hard tools.
      • Fullerenes are used as conductors.
        • It can be used as an absorber of gases.
        • Fullerenes are used as lubricants.
        • Some forms of fullerenes are used in making cosmetics-related ingredients.
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