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GATE 2019 CY – Question 13

Inorganic Chemistry · Main Group Elements: Shapes and structures of molecules using VSEPR postulates, Hydrides, halides, oxides, oxoacids, nitrides, sulfides - shapes and reactivity. Structure and bonding of boranes, carboranes, silicones, silicates, boron nitride, borazine and phosphazenes: electron counting in polyhedral boranes, isolobal analogy. Allotropes of carbon, phosphorus and sulfur. Industrial synthesis of compounds of main group elements such as NH3, H2SO4 and HNO3. Chemistry of noble gases and interhalogen compounds. Acid-base concepts and principles (Lewis, Brønsted, HSAB and acid-base catalysis). · 1 mark · Multiple choice

Which carbon allotrope has a discrete molecular structure?

  1. Diamond
  2. α-Graphite
  3. β-Graphite
  4. Fullerene

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Correct answer: (D) Fullerene

Explanation

Diamond is an extended three-dimensional covalent network and the graphite forms consist of extended carbon sheets with different stacking. Fullerenes instead consist of finite cages such as C₆₀. Thus D has discrete molecules rather than an extended network.

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