Technetium-99m is used in a variety of medical applications.It has a half-life of 6 hours.If 100.0 mg of technetium-99m is prepared at 6:00 AM, how many milligrams are still active when it is needed for diagnostic testing at 6:00 PM?
A) 100.0 mg
B) 50.0 mg
C) 25.0 mg
D) 10.0 mg
E) 5.00 mg

Question

Quizplus · Accepted Answer

Technetium-99m has a half-life of 6 hours, meaning half of it decays every 6 hours. From 6:00 AM to 6:00 PM is 12 hours, or two half-lives. After the first half-life (6 hours), 50.0 mg would remain. After the second half-life (another 6 hours), half of that, or 25.0 mg, would remain.

Technetium-99m Is Used in a Variety of Medical Applications