Avogadro's constant: Difference between revisions
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The [[SI]] definition of '''Avogadro's constant''' (designated ''N''<sub>A</sub>) is: the number of entities (such as atoms, ions, or molecules) per [[mole (unit)|mole]]. (This definition requires a definition of mole that does not rely on ''N''<sub>A</sub>, but one that is in terms of <sup>12</sup>C atoms). | |||
:''See for more details [[Avogadro's number]].'' | |||
The [[SI]] definition of '''Avogadro's constant''' (designated ''N''<sub>A</sub>) is: the number of entities (such as atoms, ions, or molecules) per [[mole (unit)|mole]]. (This definition requires a definition of mole that does not rely on ''N''<sub>A</sub>, but one that is in terms of <sup>12</sup>C atoms). The constant ''N''<sub>A</sub> has dimension mol<sup>−1</sup>. | |||
The numeric value of Avogadro's constant is ''N''<sub>A</sub> = 6.022 141 79 x 10<sup>23</sup> mol<sup>−1</sup>. | The numeric value of Avogadro's constant is ''N''<sub>A</sub> = 6.022 141 79 x 10<sup>23</sup> mol<sup>−1</sup>. | ||
Because the mole and Avogadro's number are defined in terms of the atomic mass constant (one twelfth of the mass of a <sup>12</sup>C atom), Avogadro's ''constant'' and ''number'' have by definition the same numerical value. In practice the two terms are used interchangeably. | Because the mole and Avogadro's number are defined in terms of the atomic mass constant (one twelfth of the mass of a <sup>12</sup>C atom), Avogadro's ''constant'' and ''number'' have by definition the same numerical value. In practice the two terms are used interchangeably. | ||
Revision as of 10:16, 24 June 2009
- See for more details Avogadro's number.
The SI definition of Avogadro's constant (designated NA) is: the number of entities (such as atoms, ions, or molecules) per mole. (This definition requires a definition of mole that does not rely on NA, but one that is in terms of 12C atoms). The constant NA has dimension mol−1. The numeric value of Avogadro's constant is NA = 6.022 141 79 x 1023 mol−1.
Because the mole and Avogadro's number are defined in terms of the atomic mass constant (one twelfth of the mass of a 12C atom), Avogadro's constant and number have by definition the same numerical value. In practice the two terms are used interchangeably.