A given radioactive sample is reduced from 20 g to 1.25 g in 40 days. Its half-life would be:
Correct answer: A. 10 days
- A. 10 days
- B. 8 days
- C. 5 days
- D. 6 days
Explanation
Initial mass = 40gFinal mass = 1.25gNumber of half lives = nInitial mass x (1 / 2)n = final mass(1 / 2)n = final mass / initial mass ==> 0.5n = 1.25 / 200.5n = 0.0625 ==> 0.54 = 0.0625n = 4Total number of days = 40Half life = 40 / n ==> half life = 40 / 4 =10
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