Deck 30: Nuclear Energy and Elementary Particles: Part A

Question 1

10¹⁰ Bq = ______ Ci?

A) 2.7 × 10^-11
B) 3.7
C) 0.27
D) 3.7 × 10¹⁰

Answer 1

0.27

Question 2

A pure sample of ²²⁶Ra contains 3.0 × 10¹⁴ atoms of the isotope.If the half-life of ²²⁶Ra = 1.6 × 10³ years,what is the activity of this sample?

A) 13 × 10¹⁰ decays/yr
B) 9.4 × 10¹⁰ decays/yr
C) 6.7 × 10⁹ decays/yr
D) 8.7 × 10¹⁰decays/yr

Answer 2

13 × 10¹⁰ decays/yr

Question 3

Approximately how many half-life periods must elapse if the activity of a radioactive isotope sample is to be reduced to 0.03 of the original value?

A) 5
B) 3
C) 8
D) 60

Answer 3

5

Question 4

A pure sample of ²²⁶Ra contains 3.0 × 10¹⁴ atoms of the isotope.If the half-life of ²²⁶Ra = 1.6 × 10³ years,what is the decay rate of this sample? (1 Ci = 3.7 × 10¹⁰ decays/s)

A) 2.7 × 10−¹² Ci
B) 11 × 10−⁸ Ci
C) 3.4 × 10−¹⁰ Ci
D) 7.4 × 10−⁸ Ci

Question 5

The half-life of radioactive Technetium-99 is 6.0 hours.Find the number of ⁹⁹Tc nuclei necessary to produce a sample of activity 18 µCi.(1 Ci = 3.7 × 10¹⁰ decays/second)

A) 1.2 × 10⁹
B) 3.4 × 10¹¹
C) 8.0 × 10⁸
D) 2.1 × 10¹⁰

Question 6

Approximately how many radioactive atoms are present in a tritium sample with an activity of 0.6 × 10−⁶ Ci and a half-life of 12.3 years? (1 Ci = 3.7 × 10¹⁰ decays/s)

A) 4 × 10¹⁰
B) 2 × 10⁸
C) 7 × 10⁸
D) 1 × 10¹³

Question 7

The isotope ⁶⁴Zn has a nuclear radius of 4.8 × 10−¹⁵ m.Approximately what is the nuclear radius of the isotope ¹²⁵Te?

A) 2.0 × 10−¹⁵ m
B) 3.6 × 10−¹⁵ m
C) 2.7 × 10−¹⁵ m
D) 6.0 × 10−¹⁵ m

Question 8

The relationship
,where A is the mass number of a nucleus and r is it radius,implies which of the following about nuclei?

A) Nuclei are cubic.
B) Different nuclei have the same density.
C) Neutrons in nuclei attract each other even though they have no charge.
D) Nuclei tend to have the same ratio of protons to neutrons.

Question 9

Over the course of 6 hours,15% of a radioactive material decays.What is its half-life?

A) 12.8 hrs
B) 25.6 hrs
C) 4.1 hrs
D) 68.6 hrs

Question 10

Neglecting recoil of the gold nucleus,how much kinetic energy must an alpha particle (charge = 2 × 1.6 × 10−¹⁹ C)have to approach to within 1.95 × 10−¹⁴ m of a gold nucleus (charge = 79 × 1.6 × 10−¹⁹ C)? (k_e = 8.99 × 10⁹ N⋅m²/C² and 1 MeV = 1.6 × 10−¹³ J)

A) 14.6 MeV
B) 11.7 MeV
C) 18.2 MeV
D) 22.7 MeV

Question 11

The isotope ⁶⁴Zn has a nuclear radius of 4.8 ×10−¹⁵ m.Which of the following is the mass number of an isotope for which the nuclear radius is 6.8 ×10−¹⁵ m?

A) 182
B) 125
C) 145
D) 96

Question 12

Tritium has a half-life of 12.3 years.What proportion of its original radioactivity will a sample have after 6 years?

A) 0.55
B) 0.60
C) 0.84
D) 0.71

Question 13

If a fossil bone is found to contain 1/16th as much Carbon-14 as the bone of a living animal,what is the approximate age of the fossil? (half-life of ¹⁴C = 5730 years)

A) 7640 years
B) 22,900 years
C) 45,800 years
D) 17,200 years

Question 14

Tritium has a half-life of 12.3 years.How many years will elapse when the radioactivity of a tritium sample diminishes to 30% of its original value?

A) 29 years
B) 21 years
C) 86 years
D) 57 years

Question 15

An ancient building was known to have been built 4000 years ago.Approximately what proportion of Carbon-14 atoms are still in the building's wooden framing compared to the number which were present at the time of its construction? (half life of ¹⁴C = 5730 years)

A) 0.696
B) 0.616
C) 0.500
D) 0.425

Question 16

Sample #1 is made from an isotope with decay constant
And sample #2 is made from an isotope with decay constant
,where
)Which of the following statements must be true?

A) The activity of sample #2 is greater than that of sample #1.
B) The activity of sample #1 is greater than that of sample #2.
C) The half-life exhibited for sample #1 is greater than that of sample #2.
D) The half-life exhibited for sample #2 is greater than that for sample #1

Question 17

If there are 146 neutrons in ²³⁸U,how many neutrons are found in the nucleus of ²³³U?

A) 147
B) 145
C) 143
D) 141

Question 18

Certain stars at the end of their lives are thought to collapse,combining their protons and electrons together to form a neutron star.Such a star could be thought of as a giant atomic nucleus.If a star of mass equal to M = 4.00 × 10³⁰ kg collapsed into neutrons (m_n = 1.67 × 10−²⁷ kg),what would be the radius of such a star? (Hint: r = r₀A^1/3,where r₀ = 1.20 × 10−¹⁵ m. )

A) 12.7 km
B) 25.4 km
C) 16.1 km
D) 18.5 km

Question 19

Tritium is radioactive with a half-life of 12.33 years decaying into ³He with low-energy electron emission.If we have a sample of 2.35 × 10¹⁹ tritium atoms,what is its activity in decays/second? (1 year = 3.16 × 10⁷ s)

A) 6.64 × 10⁷/second
B) 5.35 × 10⁹ /second
C) 3.69 × 10⁸/second
D) 4.18 × 10¹⁰/second

Question 20

A radioactive material initially is observed to have an activity of 1000 decays/sec.If nine hours later it is observed to have an activity of 125 decays/s,what is its half-life?

A) 1/2 hour
B) 8 hours
C) 3 hours
D) 1 hour

Question 21

The half-life of ¹⁹N is 0.42 s.What is the decay constant for this isotope?

A) 1.7 × 10^-11 Ci
B) 1.7 s^-1
C) 1.1 s^-1
D) The decay constant is not defined for a half-life of less than one second.

Question 22

Tritium (³H)has a half-life of 12.3 years and releases 0.0186 MeV energy per decay.What is the rate at which energy is released for a 3.0-gram sample of tritium? (N_A = 6.02 × 10²³ mol^-1,1 year = 3.16 × 10⁷ s,1 MeV = 1.6 × 10^-13 J,and m_t = 3.01605 u)

A) 3.2 W
B) 1.1 W
C) 9.6 W
D) 0.33 W

Question 23

Tritium (³H)has a half-life of 12.3 years and releases 0.0186 MeV energy per decay.What is the activity of a 9.0-gram sample of tritium? (N_A = 6.02 × 10²³ mol^-1,1 year = 3.16 × 10⁷ s,1 MeV = 1.6 × 10^-13 J,and m_t = 3.01605 u)

A) 1.3 × 10¹⁶ Bq
B) 1.1 × 10¹⁵ Bq
C) 3.6 × 10¹⁴ Bq
D) 3.2 × 10¹⁵ Bq

Question 24

What particle is emitted when ²³⁶Pa decays to ²³⁶U? (The atomic numbers of Pa and U are,respectively,91 and 92. )

A) beta (positron)
B) alpha
C) gamma quantum
D) beta (electron)

Question 25

About what fraction of the initial activity of a radioactive source remains after 10 half-lives?

A) 1.0 × 10^-10
B) 9.8 × 10^-4
C) 5.0 × 10^-2
D) 3.9 × 10^-3

Question 26

A deuteron is captured by an oxygen-16 atom which in turn emits a proton.What is the element and mass number of the product isotope?

A) oxygen-15
B) fluorine-15
C) nitrogen-15
D) oxygen-17

Question 27

The energy released from a nuclear reaction is equal to:

A) energy associated with momentum conservation.
B) the exothermic endothermy.
C) energy associated with the change in mass.
D) the total charge involved.

Question 28

What energy must be added or given off in a reaction where a helium atom is separated into two hydrogen atoms and two neutrons? (Atomic masses for each: hydrogen,1.007825 u;neutron,1.008665 u;helium,4.002602 u;also,1 u = 931.5 MeV/c². )

A) 28.3 MeV given off
B) 20.7 MeV added
C) 20.7 MeV given off
D) 28.3 MeV added

Question 29

What is the energy released for the reaction where the products are 0.0051 u less than the reactants? (1 u = 931.5 MeV/c²)

A) 7.6 MeV
B) 5.2 MeV
C) 4.8 MeV
D) 8.5 MeV

Question 30

Calculate the binding energy per nucleon of the Nucleus,given that the mass of this nucleus is 3.016029 u.(m_p = 1.007276 u,m_n = 1.008665,and 1 u = 931.5 MeV/c²)

A) 2.66 MeV/nucleon
B) 2.86 MeV/nucleon
C) 2.45 MeV/nucleon
D) 2.23 MeV/nucleon

Question 31

What particle is emitted when ²⁰Na decays to ²⁰Ne? (The atomic numbers of Na and Ne are,respectively,11 and 10. )

A) beta (positron)
B) gamma quantum
C) alpha
D) beta (electron)

Question 32

What is the energy released (or gained signified by the minus sign)value of the reaction
? The mass of the alpha particle is 4.002602 u,of the nitrogen is 14.003074 u,of the oxygen is 15.994915 u,and of the hydrogen is 2.014102 u.(1 u = 931.5 MeV/c²)

A) -3.11 MeV
B) -3.34 MeV
C) 3.11 MeV
D) 3.34 MeV

Question 33

In the reaction
,what are the mass number and the atomic number of the product designated by X?

A) 101,42
B) 102,44
C) 102,42
D) not given

Question 34

The isotope ²³⁸U,which starts one of the natural radioactive series,decays first by alpha decay followed by two negative beta decays.At this point,what is the resulting isotope?

A) ²³⁴Th (Z = 90 for Th. )
B) ²³⁶U
C) ²³⁸U
D) Some other uranium isotope not given above.

Question 35

One of the nuclear reactions that occurs is )What does the X represent in this equation?

A)
B)
C)
D)

Question 36

An alpha particle (mass = 6.68 × 10−²⁷ kg)is emitted from a radioactive nucleus with an energy of 6.22 MeV.How fast is the alpha particle moving in m/s? (1 MeV = 1.6 × 10−¹³ J)

A) 3.70 × 10⁶ m/s
B) 1.73 × 10⁷ m/s
C) 1.55 × 10⁷ m/s
D) 1.85 × 10⁶ m/s

Question 37

Which of the following methods of decay does not result in an element different from that of the original parent nucleus?

A) alpha followed by negative beta followed by another negative beta
B) alpha followed by beta
C) alpha followed by gamma followed by another gamma
D) alpha followed by positive beta followed by another positive beta