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Unformatted text preview: group them. Just as we often work with a dozen (12)
items such as eggs, we work with mole s of atoms. A mole is 6.02 × 1023 of anything. It is a huge number. A
mole of reams of copier paper (each 1.9 inches thick) stacked up would be 1.8 × 1019 miles high, about 1/10 of
the diameter of the Milky Way galaxy. It's only 9.2 × 107 miles from the earth to the sun. A mole of pennies is
more money than the US government spent in the 20th century.
The number 6.02 × 1023 is Avogadro's
number. This honors Amedeo Avogadro, who recognized that equal volumes of gases at the same temperature
and pressure contain equal numbers of molecules.
Since we have an extremely large number, the mole, and
these infinitesimal particles, atoms, a mole of atoms is a convenient quantity to work with in a laboratory. A mole
of helium atoms has a mass of 4 grams (a bit more than a peanut) and a mole of lead atoms has a mass of 207
grams (about the mass of a coffee mug). The mass of a mole of atoms of any element is called its molar mas s . It
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This document was uploaded on 01/22/2014.
 Spring '14
 Mole

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