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GATE 2022 CY – Question 54

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 select

The CORRECT statement(s) about the Group-I metals is(are)

  1. Reactivity of Group-I metals with water decreases down the group
  2. Among the Group-I metals, Li spontaneously reacts with N2 to give a red-brown layer-structured material
  3. Thermal stability of Group-I metal peroxides increases down the group
  4. All the Group-I metal halide are high-melting colorless crystalline solids

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Show answer and explanation

Correct answer: (B) Among the Group-I metals, Li spontaneously reacts with N2 to give a red-brown layer-structured material; (C) Thermal stability of Group-I metal peroxides increases down the group; (D) All the Group-I metal halide are high-melting colorless crystalline solids

Explanation

Water reactivity generally increases down the group, soAfalse. Lithium uniquely reacts readily with nitrogen to give red-brown layeredLi3N, Btrue. Larger cations stabilize larger peroxide anions, so peroxide thermal stability increases down the group, C true. The listed alkali halides are colourless crystalline high-melting salts, D true. **Select B, C, D**.