A sample of radioactive isotope I is to be used for medical diagnosis of the kidneys. The isotope has a half-life of 8.0 days, and the sample is required to have an activity of 8 x 10^5 per second at the time it is given to the patient. Calculate the mass of the I-131 present in the sample.
a) at the time it is given (which I correctly found)
b) when it is prepared 24 hours earlier
c) 24 hours after being given
I have found the decay constant to be approx 1.00 x 10^-6
Half life is 691200
Initial no. of atoms: 7.98 x 10^11
Mass at the time given : 1.74 x 10^-10
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