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Half-Life Question Problem
What is the total mass of 16 grams of 60Co that remain unchanged after 15.9 years? • Reffy, Table N (p. 6) shows that the half-life of 60Co is 5.271 years.
• One half-life = 5.271 years
• 15.9 years = 3 half-lives ( 15.9 = 3)
5.271
• Let’s figure out the mass of 60Co after 3 half-lives (when the original mass is 16):
1 half-life
2 half-lives
3 half-lives
16 = 8 2
82 = 4
42 = 2
After 3 half-lives, the mass of 60Co is 2 grams.
UNIT 12: NUCLEAR CHEMISTRY © 492
