Chapter 21
Critical Thinking Exercise
Nuclear Chemistry
The power of nuclear explosions is often reported in kilotons or megatons, meaning equivalent to
the explosion of that mass of 2,4,6-trinitrotoluene (TNT). The first atomic bomb tested at
Alamagordo, NM was rated at 20. kilotons. Determine the mass of 235U that underwent fission in
the bomb. Assume the fission reaction is
235
1
92 U  0 n
The nuclear masses are:
1.
235
U,234.9934 u,
95
1
 139
54 Xe  38 Sr  2 0 n
Xe, 138.8891 u, 95Sr, 94.8985 u, 1n, 1.0087 u.
139
The balanced chemical reaction for the explosion of TNT is given below.
2C7H5N3O6(s)  10C(graphite) + CO(g) +3 CO2(g) + 3 N2(g) + 5H2O(g)
Give Hr for a TNT explosion. Hf for TNT = –65.5 kJ/mol; Hf for CO(g) = -110.0
kJ/mol; Hf for CO2(g) = -393.5 kJ/mol; Hf for H2O(g) = -241.8 kJ/mol.
a. +2368.5 kJ
d. –3459.4 kJ
b. –2368.5 kJ
e. –34594.2 kJ
c. +3459.4 kJ
Chapter 21
2. How much energy is released when 20. kilotons of TNT explode? (molar mass of TNT =
227.14 g/mol)
a. 9.5 x 1010 kJ
b. 1.9 x 1011 kJ
d. 1.9 x 108 kJ
c. 9.5 x 107 kJ
e. 1.2 x 108 kJ
3. What is the change in mass for the fission reaction?
a.-0.4309 u
b. –0.1123 u
d.-0.3268 u
c. –0.5321 u
e. –0.1971 u
U nucleus? Use E = mc2 where c
4. What is the energy released during the fission of one
= 3.00 x 108 m/s and 1 u = 1.6605 x 10-27 kg.
a. 2.95 x 10-11 J
b. 6.44 x 10-11 J c. 7.95 x 10-11 J
d. 1.68 x 10-11 J
e. 4.88 x 10-11 J
5. What is the total energy released when 1 mole of
a. 1.01 x 1010 kJ/mol
235
U nuclei undergo fission?
235
b. 2.94 x 1010 kJ/mol c.1.78 x 1010 kJ/mol
d. 4.79 x 1010 kJ/mol
e. 3.88 x 1010 kJ/mol
6. How much 235U must undergo fission to produce the same amount of energy as 20.
kilotons of TNT?
a. 2.5 kg
b. 1.3 kg
c. 4.0 kg
7. What is the ratio of energy released by one mole of
mole of TNT exploding?
a. 106:1
8.
b. 108:1
c. 5.5 x 106:1
d. 1.6 kg
235
e. 5.4 kg
U undergoing fission to that of one
d. 7.5 x 106:1
e. 1.5 x 107:1
I has a decay constant of 0.0525 hr -1. At 6:00 AM the radioisotope generator kicked
out a preparation measuring 4.5 mCi in 34.2 mL. How hot is the preparation at 6:00
PM?
a. 1.8 mCi
b. 2.1 mCi
c. 2.4 mCi
d. 3.7 mCi
e. 4.1 mCi
123
9. A patient needs a dose of 20. µCi at 2:00 PM the same day. How many mL of solution
should be sent out at 6:00 AM so the patient will receive the correct dose?
a. 3.4 mL
b. 2.3 mL
c. 0.74 mL
d. 0.44 mL
e. 0.23 mL
10. How many days will it take for the radiation to reach a safe level?
a. 0.50 days
b. 1.5 days
c. 2.0 days
d. 3.0 days
e. 5.5 days
2