11. Nuclear Chemistry

The half-life of arsenic-74 is about 18 days. If a sample initially contains 100.00 mg arsenic-74, what mass (in mg) would be left after 72 days?

The half-life of iodine-131, an isotope used in thyroid therapy, is 8.021 days. What percentage of iodine-131 remains in a sample that is estimated to be 40.11 days old?

What is the concentration of a CO₂ in a container after 4 half-lives if 0.325 mol of CO2 is initially placed into a 5.0 L reaction vessel?

What is the half-life of the radioisotope that shows the following plot of remaining percentage vs. time?

For each of the following, indicate if the number of half-lives elapsed is:

1. one half-life

2. two half-lives

3. three half-lives

c. a sample of Au-198 with a half-life of 2.7 days after 5.4 days

Strontium-85, used for bone scans, has a half-life of 65 days.

b. How long will it take for the radiation level of strontium-85 to drop to one-eighth of its original level?

Fluorine-18, which has a half-life of 110 min, is used in PET scans.

b. If 100. mg of fluorine-18 is shipped at 8:00 a.m., how many milligrams of the radioisotope are still active when the sample arrives at the radiology laboratory at 1:30 p.m.?

What does it mean when we say that strontium-90, a waste product of nuclear power plants, has a half-life of 28.8 years?

Use the following decay curve for iodine-131 to answer problems a to c:

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b. Complete the number of days on the horizontal axis.

Harmful chemical spills can often be cleaned up by treatment with another chemical. For example, a spill of H₂SO₄ might be neutralized by addition of NaHCO₃. Why is it that the harmful radioactive wastes from nuclear power plants cannot be cleaned up as easily?

The half-life for the radioactive decay of Ce-141 is 32.5 days. If a sample has an activity of 4.0 µCi after 130 days have elapsed, what was the initial activity, in microcuries, of the sample?