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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2025 · Paper I

Q6(b)(i). Arrhenius temperature from half-life

Question

A first-order reaction has Ea = 104500 J mol⁻¹ and A = 5 × 10¹³ s⁻¹. Find the temperature at which its half-life is 60 s.

Answer in brief

T ≃ 349.1 K, or 76.0 °C.

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Topic notes: Arrhenius equation, collision theory and transition-state theory, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversArrhenius equationhalf-life first orderactivation energypre-exponential factor

All parts of Question 6