Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive so

Question

Iridium-192 is one radioisotope used in brachytherapy, in which a radioactive source is placed inside a pattern's body to treat cancer. Brachytherapy allows the use of a higher than normal close to be placed near the tumor while lowering the risk of damage to healthy tissue. Iridum-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 indium-192, shown below. Click on the graph and move the mouse over a port to get values for that point.

Explanation / Answer

from the graph we can see that

at t= 0 , sample = 100

at t = 130 , sample = 30

we know that

for radioactive decay

ln ( N/No) = -kt

so

ln ( 30/100) = -k x 130

k = 9.26133 x 10-3

so

the value of rate constant is 9.26133 x 10-3 day-1

a)

now

ln (N/No) = -kt

given

intial amount (No) = 5.5

time = 55 days

so

ln ( N/5.5) = -9.26133 x 10-3 x 55

ln(N/5.5) = -0.50937

N/5.5 = 0.600872

N = 3.3048

so

after 55 days , 3.3048 g of the original sample remains

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