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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 · 2025 · Paper I

Q5(c). Surface area of charcoal from a nitrogen monolayer

Question

At 0 °C and 1 atm pressure, the volume of nitrogen (N₂) gas required to form a monolayer on a sample of charcoal is 155.5 cm³ g⁻¹ of charcoal. Calculate the surface area per gram of charcoal. Area of cross-section of a N₂ molecule is 0.160 nm². Given: NA = 6.022 × 10²³ mol⁻¹; molar volume of gas (at 0 °C and 1 atm), Vm = 22.414 dm³ mol⁻¹.

Answer in brief

Surface area = 668 m² g⁻¹.

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Topic notes: adsorption isotherms, heterogeneous catalysis and colloids, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversmonolayer adsorptionspecific surface areanitrogen adsorptionactivated charcoalBET surface area

All parts of Question 5