Chemistry 1, H/G
Name:
Practice 2: Nuclear Problems
Date:
Per:
I.
Half-life(t1/2) & amount of radioisotope that remains [At = A0 (1/2)n], where n = # of t1/2.
1.
A radon isotope is an alpha-emitter with a half-life of 3.8 days. What is the mass of Rn-222 that remains
after 15.2 days in a sample of the gas containing 4.38g of the radioisotope? (ans. 0.27g)
2.
What is the fraction of an isotope of Co-60 that remains after 3 half-lives? What is this in percent?
3.
Radium-224 undergoes alpha emission with t1/2 = 3.64 days. Starting with a 5.00 g sample, what % remains
radioactive after 7.00 days? (ans. 26.4%)
4.
Strontium-90 decays through beta emission. After 58 years, it is found that 25% of the original sample
remains. What is the half-life of strontium-90? (ans. 29 years)
5.
Calculate the time required for three-fourths of a sample of cesium-138 to decay given that its half-life is
32.2 minutes. (ans. 64.4 min)
6.
Calculate the half-life of cesium-135 if seven-eighths of a sample decays in 6.0 x 106 years. (ans. 2.0 x 106
years)
7.
How many milligrams decay of a 15.000mg sample of radium-224 after 6396y if the half-life of the
radioisotope is 1599y? (ans. 14.063mg)
8.
The half-life of tritium is 12.3y. How long will it take for seven-eighths of the sample to decay? (ans.
36.9y)
9.
The half-life of radium-224 is 3.66d. What was the original mass of the radioisotope if .0500g remains after
7.32d? (ans. 0.200g)
©T. M. Chipi, instructor
1
Chemistry 1, H/G
Name:
Practice 2: Nuclear Problems
Date:
Per:
II. Solve the following nuclear reactions problems. Show all of your work!
1.
The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the mass defect (in amu) of
a 60Ni nucleus? (The mass of a nickel-60 nucleus is 59.9308 amu.) (ans. 0.5505)
2.
The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the mass defect (in amu) of
60
a 27 Co nucleus? (The mass of a cobalt-60 nucleus is 59.9338 amu.) (ans. 0.5489)
3.
The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the binding energy (in J) of
60
a 27 Co nucleus? (The mass of a cobalt-60 nucleus is 59.9338 amu.) (ans. 8.206 x 10-11)
4.
The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the binding energy per
60
nucleon (in J) of a 27 Co nucleus? (The mass of a cobalt-60 nucleus is 59.9338 amu.) (ans. 1.368 x 10-12)
€
€
€
5.
The mass of a proton is 1.673 x 10-24 g. The mass of a neutron is 1.675 x 10-24 g. The mass of the nucleus of an
56
Fe atom is 9.289 x 10-23 g. What is the nuclear binding energy (in J) for 56Fe? (ans. 7.72 x 10-11)
6.
When two atoms of 2H are fused to form one atom of 4He, the total energy evolved is 3.38 x 10-12 J. What is the
total change in mass (in kg) for this reaction? (ans. 3.76 x 10-29)
7.
Carbon-11 decays by positron emission: Write the balanced nuclear equation for this reaction.
__________________________________________________________________________________________
8.
The decay above occurs with a release of 2.87 x 1011 J per mole of carbon-11. When 4.00 g of carbon-11
undergoes radioactive decay, _________________________ g of mass is converted to energy. (ans.1.16 x 10-3)
9.
How much energy (in J) is produced when 0.082 g of matter is converted to energy? (ans.7.4 x 1012)
©T. M. Chipi, instructor
2