Radioactive Decay And Acid Dissociation Constant Chap. 9 And 10 Worksheet With Answers - Middle Tennessee State University Page 20
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20SOLUTIONS TO CHEMISTRY FOR THOUGHT
10.62 One (unrealized) goal of ancient alchemists was to change one element into
another. Do such changes occur naturally? Explain your reasoning.
Solution
Yes. In naturally occurring and decay, the radioisotope changes from one
kind of atom into a different kind of atom.
10.63 Refer to Figure 10.2. Some isotopes used as positron emitters in PET scans are
fluorine-18, oxygen-15, and nitrogen-13. What element results in each case
when a positron is emitted?
Solution
10.64 Consider the concept of half-life and decide if, in principle, a radioactive isotope
ever completely disappears by radioactive decay. Explain your reasoning.
Solution
In principle, no. Half of the remaining radioisotope decays each half-life.
Eventually, a condition will be reached where there is only a single atom left,
which would finally decay.
10.66 Nuclear wastes typically have to be stored for at least 20 half-lives before they
are considered safe. This can be a time of hundreds of years for some isotopes.
With that in mind, would you consider sending such wastes into outer space a
responsible solution to the nuclear waste disposal problems? Explain your
answer.
Solution
Sending nuclear wastes into space, ultimately to reach the sun, is a possible
solution. But the risk of launch failure has to be small enough to be an
acceptable risk. A launch failure would spread the radioactivity into the
environment of the Earth.
10.68 Uranium-238 is the most abundant naturally occurring isotope of uranium. It
undergoes radioactive decay to form other isotopes. In the first three steps of
this decay, uranium-238 is converted to thorium-234, which is converted to
protactinium-234, which is converted to uranium-234. Assume only one particle
in addition to the daughter is produced in each step, and use equations for the
decay processes to determine the type of radiation emitted during each step.
Solution
Step 1. U-238 Th-234 +
Step 3. Pa-234 U-234 +
-
Step 2. Th-234 Pa-234 +
-
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