Answer to Question #333539 in General Chemistry for DIVI

Question

5. A 0.400 mg initial sample of radioactive iodine–123, used to treat thyroid cancer, decreases to 0.113 mg after 24.0 hrs. Determine the half–life of iodine–123. 

Answer 1

m = m₀2^-t/T

m/m₀ = 0.400 mg / 0.113 mg = 1/4

2^-24/T = 1/4

2^-24/T = 2^-2

-24/T = -2

T = 12 hrs