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Examoogle • User • info@examoogle.com • EE-2024-8821
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1 atomic mass unit is equal to
1.66×10°−27 kg
1.66×10°−25 kg
1.66×10°−17 kg
1.66×10°−10 kg
1.66×10°−27 kg
The atomic mass unit (amu or u), also known as the unified atomic mass unit, is defined as exactly 121 of the mass of an unbound neutral atom of carbon-12 at rest and in its ground state. Numerically, this constant is equivalent to 1.660539×10°−27 kg.
The atomic mass unit (amu or u), also known as the unified atomic mass unit, is defined as exactly 121 of the mass of an unbound neutral atom of carbon-12 at rest and in its ground state. Numerically, this constant is equivalent to 1.660539×10°−27 kg.
1u=12NAMC−12≈1.66×10°−27 kg
E=mc2 — used to equate mass difference in nuclei to energy in MeV
The value is derived by dividing the molar mass of Carbon-12 (12 g/mol) by Avogadro's number (NA≈6.022×10°23 atoms/mol) and then converting grams to kilograms. Since 1 mole of Carbon-12 is 0.012 kg, 1u=6.02214076×10°23 mol−10.012 kg/mol≈1.6605×10°−27 kg.
It acts as a standard unit for measuring the mass of subatomic particles like protons and neutrons.
The mass of a proton is approximately 1.007u and a neutron is 1.008u.
In nuclear physics, energy equivalents are often expressed as 1u≈931.5 MeV/c2.
Simplifies calculations of molecular and atomic masses.
Provides a consistent bridge between microscopic mass and macroscopic chemical units.
Nuclear binding energy calculations in power plants.
Mass spectrometry analysis.
Quantum chemistry and molecular dynamics.
The value 1.66×10°−27 kg is standard for undergraduate physics.
Options B, C, and D provide powers of ten that are physically inconsistent with the mass of subatomic particles.
A is correct — The value of 1 atomic mass unit is defined as 1.66×10°−27 kg.
Remember that 1u is roughly the mass of one nucleon (proton or neutron); this helps quickly identify the order of magnitude in exam questions.