a) If the initial sample is 3.50 g, what mass of the original iridium-192 remain
ID: 834547 • Letter: A
Question
a) If the initial sample is 3.50 g, what mass of the original iridium-192 remains after 150 days?
b) Estimate the half-life of the radioisotope.
c) How many days would it take for three-fourths of the sample to decay?
Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive source is placed inside a patient's body to treat cancer. Brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. Iridium-192 is often used in the head or breast. Answer the following three questions (a, b, and c) based on the radioactive decay curve of iridium-192, shown below. Click on the graph and move the mouse over a point to get values for that point.Explanation / Answer
from the graph we can estimate that the thalf life = 70 days
so Kt = ln initial/final
= ln 2*150 /70 = ln [3.50/x]
= x = 0.79 gms
time * K = ln [1/0.25]
= ln 2 * time /70 = ln 4
= time = 140 days
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