# The Mole_

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```					THE MOLE!
Chapter 7.1
Chemcat 13.3 :

   If I give you a balance, a single penny, and a large
bag of pennies, could you figure out how many
pennies are in the bag without counting them?
Big measurements… Small measurements…
   If I use the mass of one
penny, I could compare
that to the mass of the
bag of pennies.

   I could divide the bag’s
mass by the mass of the
one penny to see how
many pennies are in my
bag.
Background:
   Counting all of the pennies would take a
very long time, and would not be
practical.

   In Chemistry, we need to be able to count
things even smaller than that, like atoms or
molecules.

   To make that easier, chemists use a unit
that can count many particles at once.
The Mole

   A mole (mol) is a unit to count the amount
of particles in a substance.
   Particles could be atoms, molecules, ions.
   Just like grams, it is a way to measure mass.
   A mole is equal to 6.02 x 1023 particles.
   The number 6.02 x 1023 is named
   In honor of Amedeo Avogadro di Quaregna.
   He studied the difference between atoms
and molecules, but did not calculate this
number himself.
Representative Particle

   A representative particle is the smallest
piece represented by a substance.
   Normally for elements
   This is an atom.
   However, some elements are found bonded
in pairs, like O2 or H2.
   The representative particle for these elements
would be a molecule.
Here comes some more math!
   The mole and Avogadro’s number can be used like
conversion factors.
   1 mole = 6.02 x1023 particles/atoms/ molecules

   How many moles of magnesium is in 1.25 x 1023
atoms of magnesium?
How many moles of magnesium is in 1.25 x 1023 atoms of
magnesium?

   What you know:
 1.25 x 1023 atoms
 1 mol Mg = 6.02 x 1023 atoms Mg

I am solving for moles of Mg.

I get .208 mol Mg
How many moles are in 2.80 x 1024 atoms
of silicon?
   What you know:
 2.80 x 1024 atoms Si
 1 mol Si = 6.02 x 1023 atoms Si

I am solving for moles of Si

I get 4.65 mol Si
How many molecules are in 0.360 mol of
water?
   What you know:
 0.360 mol water
 1 mol water = 6.02 x 1023 molecules water

   I am solving for molecules of water

   I get 2.17 x 1023 molecules of water

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 views: 6 posted: 2/11/2012 language: pages: 10