physics : class12 Electron Mass : Mass Defect : Atoms and Nuclei MCQ Questions and Answers
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Electron Mass
MCQ questions and answers.
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MCQ Questions
1. What is the approximate rest mass of an electron?
A.
9.1 × 10^-31 kg
B.
1.67 × 10^-27 kg
C.
1.67 × 10^-31 kg
D.
9.1 × 10^-27 kg
Correct Answer:
9.1 × 10^-31 kg
Explanation:
The rest mass of an electron is approximately 9.1 × 10^-31 kg.
2. What is the approximate mass of an electron in atomic mass units?
A.
0.0005486 u
B.
0.5486 u
C.
1.0000 u
D.
9.109 u
Correct Answer:
0.0005486 u
Explanation:
The mass of an electron is approximately 0.0005486 unified atomic mass units (u).
3. The mass equivalent of an electron is approximately:
A.
0.511 MeV/c²
B.
1.022 MeV/c²
C.
9.1 MeV/c²
D.
938 MeV/c²
Correct Answer:
0.511 MeV/c²
Explanation:
Using E = mc², the rest-mass energy of an electron is approximately 0.511 MeV.
4. A neutral helium atom has two electrons. What is the total mass of its electrons in terms of electron mass mₑ?
A.
mₑ
B.
2mₑ
C.
3mₑ
D.
4mₑ
Correct Answer:
2mₑ
Explanation:
A neutral helium atom contains two electrons, so their total mass is 2mₑ.
5. A neutral carbon atom has atomic number 6. How many electron masses must be included when relating its atomic mass to its nuclear mass?
A.
2mₑ
B.
6mₑ
C.
12mₑ
D.
14mₑ
Correct Answer:
6mₑ
Explanation:
A neutral atom has as many electrons as its atomic number, so carbon has six electrons with total mass 6mₑ.
6. If the mass of an electron is 0.0005486 u, what is the mass of three electrons?
A.
0.0001829 u
B.
0.0005486 u
C.
0.0016458 u
D.
0.001096? u
Correct Answer:
0.0016458 u
Explanation:
The mass of three electrons is 3 × 0.0005486 u = 0.0016458 u.
7. The mass of a neutral atom is related to the mass of its nucleus mainly by:
A.
Atomic mass = nuclear mass − mass of electrons
B.
Atomic mass = nuclear mass + mass of electrons
C.
Atomic mass = nuclear mass × mass of electrons
D.
Atomic mass is always equal to nuclear mass
Correct Answer:
Atomic mass = nuclear mass + mass of electrons
Explanation:
A neutral atom consists of its nucleus and its electrons, so its mass includes the masses of all its electrons.
8. A neutral atom contains 10 electrons. If each electron has mass mₑ, what is the total electron mass?
A.
mₑ/10
B.
10mₑ
C.
mₑ + 10
D.
100mₑ
Correct Answer:
10mₑ
Explanation:
The total mass of 10 electrons is the sum of their individual masses, equal to 10mₑ.
9. Which particle has the smallest mass among an electron, proton, and neutron?
A.
Electron
B.
Proton
C.
Neutron
D.
Proton and neutron have equal smallest mass
Correct Answer:
Electron
Explanation:
An electron has a much smaller mass than either a proton or a neutron.
10. The mass of an electron is approximately what fraction of the mass of a proton?
A.
1/2
B.
1/10
C.
1/1836
D.
1/938
Correct Answer:
1/1836
Explanation:
The electron mass is approximately 1/1836 of the proton mass, showing that electron mass is very small compared with nuclear particle masses.
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