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I recognize what atomic mass represent and what molar mass represents by why is it that a substances molar mass and it’s atomic mass are usually the same number

Ex: chlorine has an atomic mass of 35.453 u and a molar mass of 35.453 g/mol

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    $\begingroup$ I like that tinge of incertitude ("usually"). Indeed, the skill of not making overly broad generalizations is rather important in a scientist. Now to the point. Long story short, this is because the units (u and g/mol) are not facts of nature; they were invented by humans, and chosen so as to be convenient. $\endgroup$ – Ivan Neretin Aug 23 '19 at 6:19
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The term mole is a short form of the German word Molekül which was coined by Ostwald in 1890s. At that time, the "atomic mass unit" did not exist. The common term at that time was gram atomic mass or gram-molecule. The original meaning of so-called was defined to be equal one gram molecule i.e, the mass of a molecule expressed in grams. Atomic mass unit came into use by the 1950s.

These values match by definition not by coincidence. Here is how Ostwald coined the concept of a "mole". In those times molecules weights were determined by colligative properties. This is a snapshot of Findlay "Principles of Inorganic Chemistry" (translation of Ostwald's work)

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