WARM-UP / SAMPLE PROBLEMS: RADIOACTIVE DECAY
How much C-14 remains after 4 half lives if 500 grams of C-14 were present when a tree
died? (Half-Life of C-14 is 5730 years)
Manganese-56 is a beta emitter with a half-life of 2.5 h. What is the mass of manganese56 in a 1.0 mg sample of the isotope at the end of 10.4 h?
Iodine – 126 is a beta emitter with a half-life of 13 days. What is the mass of iodine –
126 in a 8.0 mg sample of the isotope at the end of 39 days?
If an isotope of some element has a half-life of 15,000 years, approximately how much of
the isotope atoms in a dating sample will remain after 30,000 years?
If the half-life of a radioactive isotope is 1 billion years, and we measure a parent-todaughter ratio of 1:3 in a particular sample, (i.e. the parent is now 25% of the total) the
age of the sample would be about:
A watch contains a radioactive substance with a half-life of 1.40E10 -2 years. After 50
years only 25 mg of the substance remains. Calculate the amount originally present.