|AP Chemistry - Nuclear Worksheet #4|
|1.||What is meant
by the term half-life?
has a half-life of 28 years. How long will it take for all of the strontium-90
presently on earth to be reduced to 1/32 of its present amount?
of cesium-137 is 30 years. Of an initial 100 g sample, how much cesium-137
will remain after 300 years?
|4.||You are at a
dinner party and your host brings out a bottle of brandy for which he paid
a great deal of money because he was told that it was bottled in the time
of Napoleon (1769-1821). Since you are a research chemist you are asked
if there is any way in which the age of the brandy can be determined. You
assert that tritium(H3) dating is the way to do it. Ordinary water
contains a very small amount of tritium that is formed in the earth's atmosphere
by reactions involving cosmic rays. Tritium disintegrates by beta-emission
at a rate equal to that at which it is formed. Water exposed to the atmosphere
will contain a constant tritium content. Since brandy contains water, it
should be possible to estimate its age. Since tritium in the bottle will
not be replaced after it decays, the older the brandy, the lower its tritium
content should be. You agree to test a sample of your host's brandy. You
find that the sample has a tritium content of 30.6% of that of present-day
water. How long ago was the brandy bottled?
t½ for H3 = 12.3 years
|5.||A 24.0 g sample
of Ra-226 is supplied to a lab in the year 2000. In the year 2040, it is
noted that only 20.0 g of Ra-226 remains. What is the half-life of Ra-226?
property of radiation is used by the Geiger counter?
units (common and SI) are used to describe the activity of a sample of
|8.||What is the name
of the radiation unit that equals 1 disintegration/s?
units (common and SI) are used to describe the quantity of energy absorbed
by a mass of tissue?
|10.||Explain how it
is possible to determine the age of uranium-bearing rocks.
wastes must be stored for seven half-lives before disposal
The t1/2 = 14.26 days
a) how long must P-32 be held?
|12.||Woven rope sandals found in a cave in Oregon were analyzed by radiocarbon dating methods. The specific activity of the carbon was found to be 850 Bq/g. What is the age of these sandals? Normal activity for C-14 is 918 Bq/g and the t1/2 = 5730 y.|