### Ideal Gas Law and Kinetic Theory

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**November 21st, 2013, 5:13 pm**Molecular Mass, the Mole, and Avogadro's Number

The relationship between the atomic mass unit and the kilogram is

Macroscopic amounts of materials contain large numbers of atoms or molecules. Even in a small volume of gas, 1 cm

Thus, the number of moles n contained in any sample is the number of particles N in the sample divided by the number of particles per mole N[sub]A[/sub] (Avogadro's number):

The number n of moles contained in a sample can also be found from its mass.

Since one gram-mole of a substance contains Avogadro's number of particles (atoms or molecules), the mass of a particle (in grams) can be obtained by dividing the mass per mole (in g/mol) by Avogadro's number:

The relationship between the atomic mass unit and the kilogram is

Macroscopic amounts of materials contain large numbers of atoms or molecules. Even in a small volume of gas, 1 cm

^{3}, for example, the number is enormous. It is convenient to express such large numbers in terms of a single unit, the gram-mole, or simply the mole (symbol: mol). One gram-mole of a substance contains as many particles (atoms or molecules) as there are atoms in 12 grams of the isotope carbon-12. Experiment shows that 12 grams of carbon-12 contain 6.022 × 10^{23}atoms. The number of atoms per mole is known as Avogadro's number N[sub]A[/sub], after the Italian scientist Amedeo Avogadro (1776–1856):Thus, the number of moles n contained in any sample is the number of particles N in the sample divided by the number of particles per mole N[sub]A[/sub] (Avogadro's number):

The number n of moles contained in a sample can also be found from its mass.

Since one gram-mole of a substance contains Avogadro's number of particles (atoms or molecules), the mass of a particle (in grams) can be obtained by dividing the mass per mole (in g/mol) by Avogadro's number: