15-­‐10-­‐26 The Mole
Unit 3: Quantities in Chemical
Reactions
6.3 – The Mole
—  Chefs and bakers follow recipes that tell
them what amounts to add
—  ½ cup of flour, a dozen eggs, 2 teaspoons of milk are all
different quantities they use.
—  Chemists also follow recipes.
—  Molecules and atoms cannot be seen because they are so small
—  But, chemists can still count them!
—  A unit is used called THE MOLE
The Mole
The Mole
—  The mole is a counting unit, just like a dozen.
—  We can count eggs or shoes by dozens.
—  In a similar way, we can count the amounts of atoms by the mole.
—  One dozen shoes takes up more space than one dozen eggs because
shoes are larger. But, you still have the same amount of each.
—  In a similar way, a mole of sulfur takes up more space than a mole
of carbon, because sulfur has a larger atomic mass. But, the amount
of atoms is the same.
Same AMOUNT (of mols/ atoms) but different MASS (because
sulfur atoms are larger!)
The Mole
The Mole
—  One mole contains 602 000 000 000 000 000 000 000 OR
—  6.02 x 1023 is called Avogadro’s constant (NA), named after
the chemist Amedeo Avogadro, who determined this value by
experimentation.
—  He used carbon to figure out this value by determining that 12 g of
C-12 contain 6.02 x 1023 atoms of carbon.
6.02 x 1023 ``entities`` of a substance.
—  1 mole of water has 6.02 x 1023 molecules!
—  1 mole of potassium has 6.02 x 1023 atoms!
—  1 mole of donuts has 6.02 x 1023 donuts!
—  The mole is used to count microscopic ``entities``: atoms, ions,
molecules.
—  Mole units are mol, symbol is n
—  ie: n = 3.5 mol
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