Radiometric dating
A sample of rock was found to contain 8.23 mg of rubidium-87 and 0.47 mg of strontium-87. Calculate the age of the rock if the half-life of the decay of rubidium by beta emission is 4.7 x 1010 years
t = 3.8 x 109 years
239Pu is a nuclear waste by-product with a half-life of 24,000 years. What fraction of the 239Pu present today will be present in 1000 years?
0.973 or 97.3%
Predict the decay pathway for 90Sr. (Strontium-88 is the most abundant stable isotope for Sr.) (Strontium-90 is a particularly hazardous radioactive isotope because, as an alkali earth metal, it will substitute for calcium in bones and teeth.)
Beta emission
Balance the following reaction equations of the fission of 235U:
a. 23592U + 10n --> 8938Sr + ___ + 2 10n
a. 14554Xe
You have been tasked with performing 14C dating on several artifacts to identify potential fakes. For the following, identify if the 14C dating is consistent with the proposed age of the artifact. Carbon from living material gives 15.3 disintegrations per minute; the half-life for 14C decay is 5730 years. Assume that a 14C date ranges ~5% of the proposed age could be authentic:
A mammoth skeleton from 12,000 years ago; 3.4 disintegrations per minute
t = 12,430 years, so this could be authentic
Technetium-99 is often used for assessing heart, liver, and lung damage because certain technetium compounds are absorbed by damaged tissues. It has a half-life of 6 hours. Calculate the rate constant for the decay of 99Tc.
0.12 h-1
In the initial sequence of thorium-232 decay, an alpha particle is emitted followed by a beta particle. What is the product of these two decay steps?
232Th --> a particle + b particle + ___
Actinium-228
Balance the following reaction equations of the fission of 235U:
b. 23592U + 10n --> 13735Cs + ___ + 1 10n
b. 9837Rb
A radioactive isotope has a half-life of 73.9 hours. If a sample initially has 100,000 atoms of this isotope, how long will it take for the sample to be reduced to 25,000 atoms? To 6,250 atoms?
25,000 atoms: 147.8 hours
6,250 atoms: 295.6 hours
What quantity of energy would be produced as one atom of plutonium-238 undergoes alpha decay? The nuclide mass of 238Pu is 238.0495 amu (3.953 x 10-22 g), and the nuclide mass of uranium-234 is 234.0409 amu (3.886 x 10-22 g). Alpha particle mass is 6.4465 x 10-24 g. The speed of light is 2.998 x 108 m/s.
5.0 x 10-12 J
Balance the following reaction equations of the fission of 235U:
c. 23592U + 10n --> 14962Sm + ___ + 3 10n
c. 8430Zn