Question

Technetium-99m is a radioactive isotope commonly used in medicine as a radioactive tracer. A radioactive tracer is an isotope injected into the body to help create images for diagnosis of health

problems. Technetium-99m has a half-life of 6 hours. If a patient receives a dose of technetium-99m one morning, about what percentage of the technetium-99m will be left in the patient's body 12
hours later?
A
6.25%
B
12.5%
С
25.0%
D
93.8%​

Answer 1

C. 25.0%

Step-by-step explanation:

Radioactive decay of an atom follows the equation:

ln[A] = -kt + ln[A]₀

Where [A] could be taken as an amount of radioactive atom after time t,

k is rate constant = ln 2 / Half-Life = ln 2 / 6hours = 0.1155hours⁻¹

[A]₀ is initial amount of the isotope = 100%

Replacing:

ln[A] = -0.1155hours⁻¹ *12hours+ ln[100%]

ln[A] = 3.2192

[A] = 25.0%

Right solution is:

C. 25.0%