Radioactive Decay And Acid Dissociation Constant Chap. 9 And 10 Worksheet With Answers - Middle Tennessee State University Page 17
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20Solution
A scintillation counter counts the flashes of light as radiation strikes a
phosphor. A Geiger counter measures the pulses of electrical current as the
radiation creates a path for electricity to flow through the gas in the detector.
Medical Uses of Radioisotopes (Section 10.6)
10.29 Explain what a diagnostic tracer is and list the ideal characteristics one should
have.
Solution
A diagnostic tracer is a radioactive isotope that concentrates in a specific
organ. It should have a short, but reasonable, half-life, have a stable
daughter isotope, be non-toxic, and give off radiation that can penetrate out
of the tissue and be detected.
10.31 List the ideal characteristics of a radioisotope that is to be administered
internally for therapeutic use.
Solution
A therapeutic radioisotope administered internally should be an alpha or beta
emitter; have a half-life long enough to do the desired radiation; be non-toxic
(and have non-toxic, non-radioactive daughter isotopes); and be
concentrated by the target tissue.
10.33 Gold-198 is a emitter used to treat leukemia. It has a half-life of 2.7 days. The
dosage is 1.0 mCi/kg body weight. How long would it take for a 70 mCi dose to
decay to an activity of 2.2 mCi?
Solution
2.2 mCi = about
1 or(
1 )
5
The fraction left is
. n = 5 half - lives
32
2
70 mCi
2.7 days x 5 = 13.5 days or about 14 days
Nonmedical Uses of Radioisotope (Section 10.7)
10.35 Suppose you are planning a TV commercial for motor oil. Describe how you
would set it up to show your oil prevents engine wear better than a competing
brand.
Solution
Use a radioisotope to make the metal surfaces on two identical engines. Use
a Geiger counter to measure the radioactivity present in the oil after running
the engines for the same length of time. The one with the higher radioactivity
in the oil had more wear on the metal parts.
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