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 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 breasta) If the initial sample is 4.25 g, what mass of the original iridium-192 remains after 130 days?.a) If the initial sample is 6.25 g, what mass of the original iridium-192 remains after 85 days? b) Estimate the half-life of the radioisotope. c) How many days would it take for three-fourths of the sample to decay?

Explanation / Answer

half life of iridium is 73.83 day. The deacy of radioacitve represents 1st order kineitcs

hence ln (Mt/Mo)= -Kt, K =rate constant =0.693/ half life = 0.693/73.83 =0.009386/days

Mt= 4.25 gm and t= 130 days

ln(Mt/Mo)= -130*0.693/73.83=-1.22

(Mt/4.25)= exp(-1.22)= 0.295

Mt= mass at 130 days= 4.25*0.295= 1.25 gm

2.   MO= 6.25 gm t= 85 daysl, ln (Mt/6.25)= -85*0.693/73.83 =-0.8

Mt/6.25= exp(-0.8)= 0.45, Mt= 6.25*0.45 = 2.8125 gm

3. for three foruth of sample when gets decayed, Mt= 1/4Mo

hence ln (1/4)=-(0.693/73.83)*t, t= 148 days.

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