Assignment 3-7
Half-Life Worksheet
Complete each problem. Be sure to show all work and place final answer in the
box provided
1) Iron-59 is used in medicine to diagnose blood circulation disorders. The half life
of
iron-59 is 44.5 days. How much of a 2.00 mg
sample will remain after 133.5 days?
2) If gallium-68 has a half-life of 68.3 min, how much of a 10.0 mg sample is left
after one half life? How much is left after 3 half-lives?
3) If the passing of 5 half-lives leaves 25.0 mg of a strontium-90 sample, how much
was present at the beginning?
4) How much of a 1.0 g polonium-214 sample remains after 818 microseconds?
(the half life of polonium-214 is 163.7 microseconds)
5) The initial mass of a radioisotope is 10.0g. If the radioisotope has a half life of
2.75 years, how much remains after 4 half-lives?
6) The half life of tritium (an isotope of hydrogen) is 12.3 years. If 48.0 mg of tritium
is released from a nuclear power plant during the course of a mishap, What mass
will remain after 49.2 years? How much will remain after 98.4 years?
7) Technetium-104 has a half-life of 18.0 minutes. How much of a 165.0 g sample
remains after 90.0 min?
8) Manganeese-56 decays by beta emission and has a half-life of 2.6 hours. How
many half-lives are there in 24 hours? How many mg will
remain after 5 half lives?