Iodine-131 is administered orally in the form of NaI(aq) as a treatment for thyroid cancer. The half-life of iodine-131 is 8.04 days. How much time is required for the activity of a sample of iodine-131 to fall to 17.5 percent of its original value?

24.12 days

Explanation:

First off, let's find out how many decays the compound ; iodine131 undergoes to get to 17.5 percent of its original value.

Half life is simply the time required for a quantity to reduce to half of its initial value.

The half-life of iodine-131 is 8.04 days.

100% - 50%  (First Half life)

50%  - 25%  (Second Half life)

25%  - 17.5%  (Third Half life)

This mwans i would take three halff lives;

Time requred = 3 * Half life = 3 * 8.04 days = 24.12 days

the answer is b. dilution