23 F decays by emitting a - particle. This decay process has a half-life of 2.20

Question

23F decays by emitting a - particle. This decay process has a half-life of 2.20 s. Answer the following questions about this process and report all answers to three significant figures.



1. Determine the initial activity (in dis/s, do not input units) of a 2.32 mg sample of this isotope. Report your answer to three significant figures in scientific notation.



1.91×1019dis/s

2. Determine the time (in s) that it takes for the activity of 23F to decrease to 1.57×105 dis/s.

GOT ONLY ONE TRY LEFT !!

Explanation / Answer

2)

initial activity = 1.91 x 10^19 dis/ s

remaining = 1.57 x 10^5 dis/s

decay constant = 0.693 / half life = 0.693 / 2.20 = 0.315 sec-1

time = 1/ k * ln (Ao / At)

        = 1/ 0.315 * ln (1.91 x 10^19 / 1.57 x 10^5 )

        = 103 sec

time = 103 sec

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