Q127 · CSIR NET Chemistry, December 2011
Paper: CSIR NET December 2011 · Subject: Physical Chemistry · Chapter: Chemical Kinetics · Topic: Chemical Kinetics – General · Marks: 2 · Difficulty: Hard
The carbon-14 activity of an old wood sample is found to be 14.2 disintegrations $\mathrm{min^{-1}\,g^{-1}}$. Calculate age of old wood sample, if for a fresh wood sample carbon-14 activity is 15.3 disintegrations $\mathrm{min^{-1}\,g^{-1}}$ ($t_{1/2}$ carbon-14 is 5730 years), is:
(a)5,000 years
(b)4,000 years
(c)877 years
(d)617 years
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
t = (5730/0.693) ln(15.3/14.2) = 8268 × 0.0746 ≈ 617 years (d).
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