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The half-life of N is 6.5 s. A sample of this nuclide of hydrogen is observed for 32.5 s. The fraction of the original radioactive isotope remaining after this time is:

Correct answer: A. 1/32

  • A. 1/32
  • B. 1/16
  • C. 1/8
  • D. 1/4

Explanation

The explanation is given below: To find the fraction of the original radioactive isotope of nitrogen (N) remaining after 32.5 seconds, we can use the concept of radioactive decay and the half-life of the isotope. The half-life of N is 6.5 seconds, which means that in 6.5 seconds, half of the original sample will decay, and the other half will remain. For each successive half-life period, half of the remaining sample will decay, and the other half will persist. To calculate the fraction remaining after 32.5 seconds, we need to determine how many half-life periods have elapsed during this time. 32.5 seconds ÷ 6.5 seconds per half-life = 5 half-life periods. For each half-life period, the fraction remaining is halved, so after 5 half-life periods, the fraction remaining is (1/2)^5, which is equal to 1/32. So, after 32.5 seconds, 1/32 of the original radioactive isotope of nitrogen remains.

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About Half-life and Rate of Decay

Half-life is the time required for half the unstable nuclei in a sample to decay, and it remains constant for a particular radioactive nuclide. Questions use the exponential decay law, decay constant, activity, remaining quantity and mean life. Radioactive decay is random for individual nuclei but predictable for large samples.

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