# Problem: Another radioisotope of iodine, 131I, is also used to study thyroid function (see Follow-up Problem 16.7A). A patient is given a sample that is 1.7 x 10−4 M 131I. If the half-life is 8.04 days, what fraction of the radioactivity remains after 30. days?Follow-up Problem 16.7A. Iodine-123 is used to study thyroid gland function. This radioactive isotopebreaks down in a first-order process with a half-life of 13.1 h. What is the rate constantfor the process?

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###### Problem Details

Another radioisotope of iodine, 131I, is also used to study thyroid function (see Follow-up Problem 16.7A). A patient is given a sample that is 1.7 x 10−4 M 131I. If the half-life is 8.04 days, what fraction of the radioactivity remains after 30. days?

Follow-up Problem 16.7A. Iodine-123 is used to study thyroid gland function. This radioactive isotope
breaks down in a first-order process with a half-life of 13.1 h. What is the rate constant
for the process?