| MadSci Network: Chemistry |
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The definition of the mole is primarily concerned with being able to use
macroscopic measurements (with a scale) to deal with atomic/molecular ratios.
The mole is defined as the number of carbon atoms in 12.0000... grams of
carbon-12 because 12C is the accepted standard for atomic masses and all
atomic masses are referenced to 12C.
Relative to 12C = 12, natural sulfur has an average atomic weight of 32.06. So one mole of natural sulfur weighs 32.06 grams. This allows us to combine, say, the correct amounts (by mass) of carbon and sulfur to make carbon disulfide. We just need to make sure we have two moles of sulfur for every mole of carbon. The number of particles in a mole very seldom matters. Usually it's the molar mass that one is worried about. Anyhow, when atomic weights were determined using a different scale (natural oxygen = exactly 16) the number of particles in a mole was different, but the concept was the same.
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