Answer :
The decay of 84 Br by beta emission can be evaluated by determining the decay constant and then employing calculations to find out the mass of the nuclide in the sample. After three half-lives, one-eight of the original 84 Br will remain in the sample. The sample's decay constant or half-life is not altered by time.
The subject of the question is related to nuclear physics, particularly, the decay of a nuclide via beta emission. The nuclide in question is 84 Br which has a decay rate of 373 s-1 and a half-life of 31.8 minutes.
(a) To find the grams of 84 Br in a sample that has a decay rate of 373 s-1, we make use of a method called decay constant, λ. Calculating the decay constant, λ equals to ln(2) divided by the half-life. Converting the half-life from minutes to seconds, and then using Avogadro's number to convert atoms into moles and the gram conversion to find the mass, we get the final amount of 84 Br.
(b) After 99.9 minutes which is three half-lives, the amount of 84 Br remaining in the sample can be calculated. Since the atoms decrease by half with each half-life, after three half-lives, the amount of nuclide present will be only one-eight of the original amount.
The time or duration only affects the amount of nuclide remaining in the sample but not the decay constant or half-life.
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