*Honors Chemistry*

**Chapter 19 Study Questions**

1.
Balance each of the following nuclear equations and indicate the type of
nuclear reaction (a-emission, b-emission,
fission, fusion, or “other”).

a) _{} b) _{}

c) _{} d) _{}

e) _{} f) _{}

g) _{} h) _{}

2. The isotope _{} undergoes beta
emission with a half-life of 30 years.

a)
Write a balanced nuclear equation for this reaction.

b)
What fraction of Cs-137 remains in a sample of the isotope after 60
years?

c)
What mass of Cs will be left in a 24.0 g sample of _{} after 90 years?

d)
What fraction of Cs-137 has __decayed__ after 120 years?

3. What is the half-life of an isotope that is
75% decayed after 16 days?

4. Explain what makes an isotope
radioactive. Why do radioactive isotopes
undergo radioactive decay? How does the
energy released by nuclear reactions compare to that released by ordinary
chemical reactions? Why?

5. Write balanced nuclear equations for:

a)
positron emission by Sr-83.

b) the fusion of two C-12 nuclei to give another nucleus and a
neutron.

c) the fission of U-235 to give Ba-140, another nucleus and an __excess__
of two neutrons.

6. What new element is formed when K-40 decays
by b-emission? Is the new element formed likely to be
stable? Why or why not?

7. Why is nuclear fission considered a
“chain reaction”? What is “critical”
about critical mass? Why does nuclear
fission produce radioactive waste?

**Summary of Chapter
19: Radioactivity**

what makes elements radioactive

alpha emission

beta emission

nuclear equations

half-life

nuclear fission

production of radioactive waste

chain reaction

nuclear fusion