Some Basic Concepts of Chemistry — Chemistry STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 ScienceChemistrySome Basic Concepts of Chemistry4 Marks
Question
How is relative atomic mass of an atom measured?
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Answer
The mass of a single atom is extremely small, i.e. the mass of a hydrogen atom is $1.6736 \times 10^{-24} \ g.$ Hence, it is not possible to weigh a single atom.
In the present system, mass of an atom is determined relative to the mass of an atom of carbon$-12$ as the standard. This was decided in $1961$ by international agreement.
The atomic mass of carbon$-12$ is assigned as $12.00000$ atomic mass unit $(amu).$
The masses of all other elements are determined relative to the mass of an atom of carbon$-12 (C-12).$
The atomic masses are expressed in amu which is exactly equal to one twelth of the mass of one carbon$-12$ atom.
The value of $1 \ amu$ is equal to $1.6605 \times 10^{-24} \ g.$
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