Question

Define atomic mass unit. Why is it needed?

Answer 1

Answer:

this is the answer

Explanation:

An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12. ... The AMU is used to express the relative masses of, and thereby differentiate between, various isotopes of elements.

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Answer 2

Answer:

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We need the amu to establish the value of Avogadro's number—the number of particles in one mole. One amu is currently defined as one 12th the mass of one atom of C-12*. By definition the number of amu that equals exactly one gram is Avogadro's number.

The above convention has a several desirable consequences:

• The value of Avogadro's number can be empirically established with great percision
• The mass of 1 mole of protons, or one mole of neutrons, is very close to 1.00 g
• The mass of one mole of a particular isotope is very close to an integer
• The atomic mass in g/mol equals the atomic mass in amu/atom