physics : class12 Nuclear Packing Fraction : Mass Defect : Atoms and Nuclei MCQ Questions and Answers
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Nuclear Packing Fraction
MCQ questions and answers.
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MCQ Questions
1. The nuclear packing fraction of a nuclide is commonly defined as:
A.
(Atomic mass - mass number) / mass number
B.
(Mass number - atomic mass) / atomic mass
C.
Atomic mass × mass number
D.
Mass number / atomic mass
Correct Answer:
(Atomic mass - mass number) / mass number
Explanation:
Nuclear packing fraction is the fractional mass excess, calculated as (M - A) / A, where M is the isotopic mass in atomic mass units and A is the mass number.
2. If the isotopic mass of a nuclide is 12.012 u and its mass number is 12, its packing fraction is:
A.
0.001
B.
0.0001
C.
0.01
D.
0.1
Correct Answer:
0.001
Explanation:
Using packing fraction = (M - A) / A, we get (12.012 - 12) / 12 = 0.012 / 12 = 0.001.
3. A nuclide has atomic mass 20.020 u and mass number 20. Its packing fraction is:
A.
0.0001
B.
0.001
C.
0.01
D.
0.02
Correct Answer:
0.001
Explanation:
The packing fraction is (20.020 - 20) / 20 = 0.020 / 20 = 0.001.
4. If the packing fraction of a nuclide is positive, its isotopic mass is:
A.
Less than its mass number in atomic mass units
B.
Equal to its mass number in atomic mass units
C.
Greater than its mass number in atomic mass units
D.
Unrelated to its mass number
Correct Answer:
Greater than its mass number in atomic mass units
Explanation:
Since packing fraction is (M - A) / A, a positive value means M - A is positive. Therefore, M is greater than A.
5. If a nuclide has zero packing fraction, its isotopic mass in atomic mass units is:
A.
Twice its mass number
B.
Equal to its mass number
C.
Half its mass number
D.
Greater than its mass number
Correct Answer:
Equal to its mass number
Explanation:
For zero packing fraction, (M - A) / A = 0, so M - A = 0 and therefore M = A.
6. A nuclide has mass number 25 and packing fraction 0.002. What is its isotopic mass?
A.
25.002 u
B.
25.020 u
C.
25.050 u
D.
25.200 u
Correct Answer:
25.050 u
Explanation:
From (M - A) / A = 0.002, M - 25 = 25 × 0.002 = 0.050. Hence, M = 25.050 u.
7. A nuclide has mass number 40 and isotopic mass 39.996 u. Its packing fraction is:
8. Which nuclide has the greater packing fraction?
A.
Mass number 10, isotopic mass 10.010 u
B.
Mass number 20, isotopic mass 20.010 u
C.
Mass number 30, isotopic mass 30.015 u
D.
Mass number 40, isotopic mass 40.010 u
Correct Answer:
Mass number 10, isotopic mass 10.010 u
Explanation:
The packing fractions are 0.001, 0.0005, 0.0005, and 0.00025, respectively. Therefore, the first nuclide has the greatest packing fraction.
9. The packing fraction is usually expressed as a ratio involving:
A.
Mass excess and mass number
B.
Atomic number and neutron number
C.
Binding energy and atomic number
D.
Nuclear radius and mass number
Correct Answer:
Mass excess and mass number
Explanation:
Packing fraction is the mass excess divided by the mass number: (M - A) / A. Thus, it involves mass excess and mass number.
10. For two nuclides with the same mass number, the nuclide with the larger isotopic mass has:
A.
A smaller packing fraction
B.
The same packing fraction
C.
A larger packing fraction
D.
Zero packing fraction
Correct Answer:
A larger packing fraction
Explanation:
For the same mass number A, packing fraction is (M - A) / A. Increasing M increases the numerator while the denominator remains unchanged, so the packing fraction becomes larger.
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