Multiple choice

Atomic mass unit is a unit of mass used to express atomic & molecular weights equal to

  1. One twelfth of the mass of an atom of Carbon (C)

  2. One sixteenth of the mass of a molecule of oxygen

  3. half of the mass of the hydrogen molecule

  4. the combined mass of proton & neutron in the nucleus of a hydrogen atom.
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A Correct answer
Explanation

The atomic mass unit (amu or unified atomic mass unit, u) is defined as exactly 1/12 the mass of a neutral carbon-12 atom in its ground state. This standard was chosen because carbon-12 has six protons and six neutrons, making calculations convenient. The value is approximately 1.660539 x 10^-27 kg. Options B and C reference oxygen and hydrogen which were older standards.

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