*Chemistry*

**Chapter 19 Study Questions**

1.
Balance each of the following nuclear equations and indicate the type of
nuclear reaction (a-decay, b-decay,
g-decay,
fission or fusion).

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

b) the fission of U-235
to give Ba-140, another nucleus and three neutrons.

6.
What new element is formed when I-131 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? In a fission reaction, what is
the source of the great amount of energy that is released?

**Summary of Chapter 19: Radioactivity and Nuclear Energy**

what makes elements radioactive

alpha emission

beta emission

gamma emission

nuclear equations

band of stability

half-life (rate of decay)

nuclear fission

nuclear equation

production of radioactive waste

chain reaction

nuclear fusion