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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2023 · Paper I

Q4(d). Pyroxenes, amphiboles and phyllosilicates

Question

Pyroxenes, amphiboles and phyllosilicates are well-known groups of silicates that occur in the crust of the earth. Write the empirical formulae and draw the basic structural units of the above-mentioned silicates.

Answer in brief

Pyroxenes (SiO₃)ₙ²ⁿ⁻, single chains; amphiboles (Si₄O₁₁)ₙ⁶ⁿ⁻, double chains; phyllosilicates (Si₂O₅)ₙ²ⁿ⁻, sheets.

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Topic notes: main group chemistry: boranes, borazine, phosphazenes, silicates, silicones, interhalogens, xenon and sulfur–nitrogen compounds, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoverssilicatespyroxenesamphibolesphyllosilicatesSiO4 tetrahedronchain and sheet silicates

All parts of Question 4