An unknown sealed source contains a single radioisotope
CHEMISTRY · Multi-part · US High School · Chemistry · Atomic Structure & Nuclear · Atomic Structure & Nuclear
Problem
An unknown sealed source contains a single radioisotope. At 09:00 on Day 1 its activity is measured to be 2.50 µCi. At 09:00 on Day 3 (48 h later) the activity has fallen to 1.80 µCi. Assume the decay is first order and that no material is lost from the container.
(a) Determine the decay constant k (in h−1) and the half-life (in hours) of the isotope. Show your calculations clearly.
(b) Estimate the time, measured from 09:00 on Day 3, required for the activity of the source to decrease further from 1.80 µCi to 0.500 µCi. Express your answer in hours and in days.
(c) Suppose safety regulations require disposal of the source once its activity falls below 0.100 µCi. Calculate the total number of days from 09:00 on Day 1 until the source must be disposed of. Present your reasoning systematically.