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 G11.  KEY DEFINITIONS: AMOUNT OF SUBSTANCE, THE AVOGARDO CONSTANT 

 & THE MOLE SINCE 2018 RE-DEFINITION BY CGPM / IUPAC / IUPAP 

The key definitions below bring together material from elsewhere on this site and generally follow IUPAC and the 2018 SI re-definitions from BIPM.

Rather than being too concerned with learning definitions of these quantities, it is far more important that one is clear how to execute calculations involving key relationships between these various physical quantities, using quantity symbols appropriately, e.g., m = n M, while manipulating the SI unit symbols and derived unit symbols algebraically, i.e., g = mol x g / mol.

Of course, when important examinations are on the horizon, it would be unwise not to learn definitions as specified by any examination syllabus, but that does not demand that you understand them.

© 2021  AMOUNTofSUBSTANCE.com  &  CHEMISTRY2020.com

© 2021  AMOUNTofSUBSTANCE.com  &  CHEMISTRY2020.com

© 2021  AMOUNTofSUBSTANCE.com  &  CHEMISTRY2020.com

© 2021  AMOUNTofSUBSTANCE.com  &  CHEMISTRY2020.com

2023-Avogadro-constant-number-entities-amount-LNn-nv-final-v2-p25.png

The term molar in a chemical context means ‘divided by amount of substance’, as in molar mass, molar volume, molar charge, molar enthalpy change, etc.  This adjective preceding the name of an extensive quantity serves to generate an intensive quantity, i.e., one characteristic of the substance.

The oft-stated ‘quantity’ molar concentration epitomises incorrect use of this term: one might reasonably infer that what is being implied is amount concentration; but with unit mol / L ?

N.B.  Neither the name of the physical quantity, nor the symbol used to denote it, should imply

a particular choice of unit (IUPAC).

© 2023  AMOUNTofSUBSTANCE.com  &  CHEMISTRY2020.com

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