The half life of a radionuclide is 12.0 minutes. The time required for all except 1.25 grams of a 20.0 g sample of this nuclide to decay is ________.

Question

Quizplus · Accepted Answer

The decay process follows first-order kinetics. To find the time required for the sample to decay to 1.25 grams from 20 grams, we use the formula: $ t = n \times t_{1/2} $, where $ n $ is the number of half-lives. The fraction remaining is $ \frac{1.25}{20} = 0.0625 $. This corresponds to $ 2^{-n} = 0.0625 $, which gives $ n = 4 $. Therefore, $ t = 4 \times 12 = 48 $ minutes.

The Half Life of a Radionuclide Is 12