A sample of a radioactive element with initial mass of 24 gm decayed to 3 gm in 36 minutes. How much of the original sample remained after the first 12 minutes?
Correct answer: A. 12 g
- A. 12 g
- B. 6 g
- C. 2 g
- D. 8 g
Explanation
Mi = 24 gmf= 3 gTotal time t = 36 min24g→12g→6g→3gIt takes 3 half lives so n= 3As, n = total time/ half life 1 Half life T = t/nT =36/ 3 1 half life T= 12 min So remaining after one half life (means after 12 minutes) is 12 g
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