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UPSC Combined Geo-Scientist

Chemist

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

Mains Paper I covers inorganic chemistry.

UPSC Combined Geo-Scientist, Mains · 2024 · Mains Paper I

Q9(a). Carbon-14 activity in living carbon

Question

Calculate the activity (in dpy) due to ¹⁴C in 1.00 kg of carbon found in a living specimen. The abundance of ¹⁴C in a present-day carbon specimen is 1.3 × 10⁻¹² (t₁/₂ of ¹⁴C is 5730 y, NA = 6.023 × 10²³ atoms/mole, atomic mass of carbon = 12.011 u).

Answer in brief

Activity = 7.89 × 10⁹ disintegrations per year (approximately 7.9 × 10⁹ dpy).

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Topic notes: nuclear chemistry: radioactive decay, binding energy, radiocarbon dating and the GM counter, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverscarbon-14 activityspecific activityradiocarbondecay constantA = λN

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