Radioactive Decay And Acid Dissociation Constant Chap. 9 And 10 Worksheet With Answers - Middle Tennessee State University Page 16
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2010.13 What is meant by a half-life?
Solution
A half-life is the time required for one half of the radioactive isotopes present
at any time to undergo radioactive decay.
194
Pb , has a half-life of 11 minutes. What fraction of the lead-
10.15 An isotope of lead,
82
194 atoms in a sample would remain after 44 minutes had elapsed?
Solution
1 x
1 x
1 x
1 x = (
1 )
1
The time period, 44 minutes, is four half-life
4
=
2
2
2
2
2
16
periods. The fraction remaining is
10.17 An archaeologist sometime in the future analyzes the iron used in an old
building. The iron contains tiny amounts of nickel-63, with a half-life of 92 years.
On the basis of the amount of nickel-63 and its decay products found, it is
estimated that about 0.78% (1/128) of the original nickel-63 remains. If the
building was constructed in 1980, in what year did the archeologist make the
discovery?
Solution
1 )
1 . n= 7 half - lives
n
Since1/128 of the original is left,(
=
2
128
7 half - lives x 92 yrs/half - life =644 yrs after 1980.The year is about 2624
Health Effects of Radiation (Section 10.4)
10.23 A radiologist found that in a 30 minute period the dose from a radioactive source
was 75 units at a distance of 12.0 m from the source. What would the dose be in
the same amount of time at a distance of 2.00 m from the source?
Solution
2
d
I
y
x
; where I
=?; I
= 75units; d
= 2.00m; d
=12.0 m
=
x
y
x
y
2
I
d
y
x
2
2
d
(12.0 m)
y
3
I
x
= 75 units x
= 2.7 x 10
units
=I
x
y
2
2
d
(2.00 m)
x
Measurement Units for Radiation (Section 10.5)
10.25 Explain why the rem is the best unit to use when evaluating the radiation
received by a person working in an area where exposure to several types of
radiation is possible.
Solution
The rem measures both the intensity of the radiation and the extent of
damage by the different types of radiation.
10.27 Describe how scintillation counters and Geiger-Muller counters detect radiation.
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