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GATE 2019 CY – Question 38

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). · 2 marks · Multiple choice

Classify I zircon ZrSiO₄, II beryl Be₃Al₂Si₆O₁₈ and III pyrophyllite Al₂(OH)₂[Si₂O₅]₂.

  1. I ortho, II cyclic, III sheet silicate
  2. I ortho, II sheet, III cyclic silicate
  3. I cyclic, II sheet, III ortho silicate
  4. I sheet, II ortho, III cyclic silicate

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Correct answer: (A) I ortho, II cyclic, III sheet silicate

Explanation

Zircon contains isolated SiO₄ tetrahedra, an orthosilicate. Beryl contains six-membered Si₆O₁₈ rings, a cyclic silicate. Pyrophyllite contains extended silicate sheets. The respective assignment ortho/cyclic/sheet is A.

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